Update syn requirement from 2 to 3

[dependabot]

Updates the requirements on syn to permit the latest version.

Release notes

Sourced from syn's releases.

3.0.2

• Add Error::new_range(start..end, "msg") (#2068, #2070)
• Add Cursor::prev_span

Commits

• 88ee7be Release 3.0.2
• 587bc20 Merge pull request #2070 from dtolnay/emptyrange
• 96801f7 Allow Error::new_range at empty cursor range
• 9dc16c9 Merge pull request #2069 from dtolnay/prevspan
• 1db76b7 Align on using impl trait across all Error constructors
• bfa1ebf Make Cursor::prev_span public
• c6ac5e5 Merge pull request #2068 from dtolnay/newrange
• 1436454 Add Error::new_range constructor taking Range<Cursor>
• 123c148 Release 3.0.1
• bc11ddd Merge pull request #2067 from dtolnay/fastpeek
• Additional commits viewable in compare view

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[github-actions]

Benchmark Comparison (PR vs main)

Results (collapse to hide)

group                                                                   new
-----                                                                   ---
Creation of 100 actors                                                  1.00   600.8±75.03µs        ? ?/sec
Creation of 1000 actors                                                 1.00      5.9±0.47ms        ? ?/sec
Waiting on 100 actors to process first message                          1.00   104.4±11.92µs        ? ?/sec
Waiting on 100000 messages to be processed                              1.00     26.6±2.63ms        ? ?/sec
Waiting on 50 messages with large data in the Future to be processed    1.00     78.4±6.51µs        ? ?/sec
Waiting on 500 actors to process first message                          1.00   388.7±48.05µs        ? ?/sec
factory_queuer_dispatch/workers/10                                      1.00  1398.0±153.13µs 349.3 KElem/sec
factory_queuer_dispatch/workers/100                                     1.00  1323.4±63.50µs 369.0 KElem/sec
large_messages/256_byte_messages                                        1.00     62.4±5.02µs 1565.7 KElem/sec
large_messages/64_byte_messages                                         1.00     58.0±3.02µs 1684.5 KElem/sec
small_messages/16_byte_messages                                         1.00     55.8±3.90µs 1748.7 KElem/sec
small_messages/32_byte_messages                                         1.00     56.7±3.43µs 1723.7 KElem/sec
small_messages/8_byte_messages                                          1.00     56.6±4.51µs 1725.5 KElem/sec
spawn_throughput/10                                                     1.00     60.0±1.51µs 162.7 KElem/sec
spawn_throughput/100                                                    1.00   392.4±11.31µs 248.9 KElem/sec

Note: a negative delta indicates the PR is faster (an
improvement); a positive delta means the PR is slower (a
regression). Benchmarks are grouped (e.g., small_messages,
spawn_throughput); the flattened list below shows every
individual comparison for clearer deltas.

=== per-benchmark breakdown ===

Creation of 100 actors
----------------------
new     1.00    600.8±75.03µs       ? ?/sec

Creation of 1000 actors
-----------------------
new     1.00       5.9±0.47ms       ? ?/sec

Waiting on 100 actors to process first message
----------------------------------------------
new     1.00    104.4±11.92µs       ? ?/sec

Waiting on 100000 messages to be processed
------------------------------------------
new     1.00      26.6±2.63ms       ? ?/sec

Waiting on 50 messages with large data in the Future to be processed
--------------------------------------------------------------------
new     1.00      78.4±6.51µs       ? ?/sec

Waiting on 500 actors to process first message
----------------------------------------------
new     1.00    388.7±48.05µs       ? ?/sec

factory_queuer_dispatch/workers/10
----------------------------------
new     1.00  1398.0±153.13µs  349.3 KElem/sec

factory_queuer_dispatch/workers/100
-----------------------------------
new     1.00   1323.4±63.50µs  369.0 KElem/sec

large_messages/256_byte_messages
--------------------------------
new     1.00      62.4±5.02µs  1565.7 KElem/sec

large_messages/64_byte_messages
-------------------------------
new     1.00      58.0±3.02µs  1684.5 KElem/sec

small_messages/16_byte_messages
-------------------------------
new     1.00      55.8±3.90µs  1748.7 KElem/sec

small_messages/32_byte_messages
-------------------------------
new     1.00      56.7±3.43µs  1723.7 KElem/sec

small_messages/8_byte_messages
------------------------------
new     1.00      56.6±4.51µs  1725.5 KElem/sec

spawn_throughput/10
-------------------
new     1.00      60.0±1.51µs  162.7 KElem/sec

spawn_throughput/100
--------------------
new     1.00    392.4±11.31µs  248.9 KElem/sec

Benchmarks run on shared CI hardware (ubuntu-latest).
Differences under ~5% may be noise.