refactor: bump rexml from 3.2.6 to 3.2.8 (#1789)

Author: dependabot[bot]

Gemfile.lock

@@ -89,13 +89,15 @@ GEM
     public_suffix (4.0.7)
     rake (13.0.6)
     redcarpet (3.6.0)
-    rexml (3.2.6)
+    rexml (3.2.8)
+      strscan (>= 3.0.9)
     rouge (2.0.7)
     ruby-macho (2.5.1)
     sassc (2.4.0)
       ffi (~> 1.9)
     sqlite3 (1.6.6)
       mini_portile2 (~> 2.8.0)
+    strscan (3.1.0)
     typhoeus (1.4.0)
       ethon (>= 0.9.0)
     tzinfo (2.0.6)