light-client-js: remove the syn version pin

[mzabaluev]

The bug this used to work around is closed and the problem
no longer seems to persist.

[codecov-commenter]

Codecov Report

Merging #1242 (84b9cc6) into main (e9c41de) will decrease coverage by 0.0%.
The diff coverage is 0.0%.

@@           Coverage Diff           @@
##            main   #1242     +/-   ##
=======================================
- Coverage   64.4%   64.4%   -0.1%     
=======================================
  Files        245     245             
  Lines      21485   21489      +4     
=======================================
  Hits       13842   13842             
- Misses      7643    7647      +4     

Impacted Files	Coverage Δ
light-client-js/src/lib.rs	1.7% <0.0%> (-0.2%)	⬇️
testgen/src/vote.rs	84.8% <0.0%> (-0.9%)	⬇️
testgen/src/commit.rs	90.6% <0.0%> (-0.7%)	⬇️
light-client-verifier/src/types.rs	38.7% <0.0%> (ø)
tendermint/src/node.rs	67.3% <0.0%> (+0.1%)	⬆️
testgen/src/header.rs	84.0% <0.0%> (+0.5%)	⬆️

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[thanethomson]

LGTM!

Would this be considered a breaking change, given the dependency update?

[mzabaluev]

Would this be considered a breaking change, given the dependency update?

I don't think so. A wasm bundle has all its Rust dependencies baked in, and the JavaScript signature of the entry point did not change either.

That said, I need to give it a suitable changelog entry.