cargo: bump syn from 1.0.86 to 1.0.88

Bumps [syn](https://github.com/dtolnay/syn) from 1.0.86 to 1.0.88.
- [Release notes](https://github.com/dtolnay/syn/releases)
- [Commits](https://github.com/dtolnay/syn/compare/1.0.86...1.0.88)

---
updated-dependencies:
- dependency-name: syn
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Cargo.lock

@@ -3690,9 +3690,9 @@ dependencies = [
 
 [[package]]
 name = "syn"
-version = "1.0.86"
+version = "1.0.88"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8a65b3f4ffa0092e9887669db0eae07941f023991ab58ea44da8fe8e2d511c6b"
+checksum = "ebd69e719f31e88618baa1eaa6ee2de5c9a1c004f1e9ecdb58e8352a13f20a01"
 dependencies = [
  "proc-macro2",
  "quote",