Brittle unum formatting tests

[filmil]

For some reason this started not when I upgraded to ICU 69.1 but a few runs later.
Disabling the specific brittle test for now.

   Compiling rust_icu_unum v0.5.0 (/src/rust_icu/rust_icu_unum)                                                                         
    Finished test [unoptimized + debuginfo] target(s) in 1.30s                                                                          
     Running unittests (/src/rust_icu/target/debug/deps/rust_icu_unum-ac8d5277297f6bad)                                                 
                                                                                                                                        
running 9 tests                                                                                                                         
test tests::format_decimal_pattern_ustring ... ok                                                                                       
test tests::format_decimal ... ok                                                                                                       
test tests::format_double_currency ... ok                                                                                               
test tests::test_available ... ok                                   
test tests::format_style_ustring ... ok                                                                                                 
test tests::format_double_with_fields ... ok                                                                                            
test tests::format_and_parse_uformattable ... ok                                                                                        
test tests::format_decimal_rulebased_ustring ... ok                                                                                     
test tests::pattern ... FAILED                                                                                                          
                                                                                                                                        
failures:                                                                                                                               
                                                                                                                                        
---- tests::pattern stdout ----                                                                                                         
thread 'tests::pattern' panicked at 'assertion failed: `(left == right)`                                                                
  left: `"#,##1.###"`,                                                                                                                  
 right: `"#,##0.###"`: in test: TestCase { source_locale: "sr-RS", is_localized: false, style: UNUM_DECIMAL, expected: "#,##1.###" }', rust_icu_unum/src/lib.rs:1020:13
stack backtrace:                                                                                                                        
   0:     0x55b9fce63470 - std::backtrace_rs::backtrace::libunwind::trace::hdcf4f90f85129e83                                            
                               at /rustc/7f4afdf0255600306bf67432da722c7b5d2cbf82/library/std/src/../../backtrace/src/backtrace/libunwind.rs:90:5
   1:     0x55b9fce63470 - std::backtrace_rs::backtrace::trace_unsynchronized::h2669e30cb82f6732                                        
                               at /rustc/7f4afdf0255600306bf67432da722c7b5d2cbf82/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x55b9fce63470 - std::sys_common::backtrace::_print_fmt::hfbda19e17f6db318
                               at /rustc/7f4afdf0255600306bf67432da722c7b5d2cbf82/library/std/src/sys_common/backtrace.rs:67:5
   3:     0x55b9fce63470 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h1a8751bf59281272
                               at /rustc/7f4afdf0255600306bf67432da722c7b5d2cbf82/library/std/src/sys_common/backtrace.rs:46:22
   4:     0x55b9fce8647f - core::fmt::write::h7aa6cd0067dca82a                                                                          
                               at /rustc/7f4afdf0255600306bf67432da722c7b5d2cbf82/library/core/src/fmt/mod.rs:1094:17 
   5:     0x55b9fce60385 - std::io::Write::write_fmt::he6661e7347cae026                            
                               at /rustc/7f4afdf0255600306bf67432da722c7b5d2cbf82/library/std/src/io/mod.rs:1580:15     
   6:     0x55b9fce6560b - std::sys_common::backtrace::_print::h551e9ec8a9fa8106                                      
...

[filmil]

For posterity, I think I know how this comes about. The CLDR data for sr-RS aren't exactly very complete, and they get updated with every major release. This means whenever these rules get more precise, some of the tests necessarily break.

I was looking at updating them, with specific focus on the spell-out of numbers, but there's quite a bit of work to get it up to snuff. I'll check whether there's someone who could be able to do that.