Bump syn from 2.0.66 to 2.0.68

Bumps [syn](https://github.com/dtolnay/syn) from 2.0.66 to 2.0.68.
- [Release notes](https://github.com/dtolnay/syn/releases)
- [Commits](dtolnay/syn@2.0.66...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>

Cargo.toml

@@ -102,7 +102,7 @@ clvm-derive = { path = "./crates/clvm-derive", version = "0.10.0" }
 chia-fuzz = { path = "./crates/chia-consensus/fuzz", version = "0.10.0" }
 blst = { version = "0.3.12", features = ["portable"] }
 clvmr = "0.7.0"
-syn = "2.0.66"
+syn = "2.0.68"
 quote = "1.0.32"
 proc-macro2 = "1.0.84"
 proc-macro-crate = "1.3.1"