Update syn requirement from 1.0.95 to 2.0.63

Updates the requirements on [syn](https://github.com/dtolnay/syn) to permit the latest version.
- [Release notes](https://github.com/dtolnay/syn/releases)
- [Commits](dtolnay/syn@1.0.95...2.0.63)

---
updated-dependencies:
- dependency-name: syn
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

positional_derive/Cargo.toml

@@ -13,5 +13,5 @@ proc-macro = true
 proc-macro-error = "1.0.4"
 proc-macro2 = "1.0.39"
 quote = "1.0"
-syn = {version = "1.0.95", features = ["extra-traits", "full"]}
+syn = {version = "2.0.63", features = ["extra-traits", "full"]}
 trybuild = "1.0.61"