Bump syn from 1.0.108 to 1.0.109 (#2621)

Bumps [syn](https://github.com/dtolnay/syn) from 1.0.108 to 1.0.109.
<details>
<summary>Commits</summary>
<ul>
<li><a href="bfa790b8e4"><code>bfa790b</code></a> Release 1.0.109</li>
<li><a href="c182545939"><code>c182545</code></a> Restore compatibility with rust 1.31</li>
<li>See full diff in <a href="https://github.com/dtolnay/syn/compare/1.0.108...1.0.109">compare view</a></li>
</ul>
</details>
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Cargo.lock

@@ -3767,9 +3767,9 @@ checksum = "73473c0e59e6d5812c5dfe2a064a6444949f089e20eec9a2e5506596494e4623"
 
 [[package]]
 name = "syn"
-version = "1.0.108"
+version = "1.0.109"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d56e159d99e6c2b93995d171050271edb50ecc5288fbc7cc17de8fdce4e58c14"
+checksum = "72b64191b275b66ffe2469e8af2c1cfe3bafa67b529ead792a6d0160888b4237"
 dependencies = [
  "proc-macro2",
  "quote",

boa_macros/Cargo.toml

@@ -14,6 +14,6 @@ proc-macro = true
 
 [dependencies]
 quote = "1.0.23"
-syn = "1.0.108"
+syn = "1.0.109"
 proc-macro2 = "1.0"
 synstructure = "0.12"