build(deps): bump syn from 2.0.67 to 2.0.68 (apache#746)

Bumps [syn](https://github.com/dtolnay/syn) from 2.0.67 to 2.0.68.
- [Release notes](https://github.com/dtolnay/syn/releases)
- [Commits](dtolnay/syn@2.0.67...2.0.68)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Cargo.toml

@@ -54,7 +54,7 @@ futures = "0.3"
 object_store = { version = "0.10.1", features = ["aws", "gcp", "azure"] }
 parking_lot = "0.12"
 regex-syntax = "0.8.1"
-syn = "2.0.67"
+syn = "2.0.68"
 url = "2.2"
 sqlparser = "0.47.0"