Update syn requirement from 1.0.0 to 2.0.42

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@1.0.0...2.0.42)

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

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

proptest-derive/Cargo.toml

@@ -34,7 +34,7 @@ criterion = "0.5"
 [dependencies]
 proc-macro2 = "1.0"
 
-syn = { version = "1.0.0", features = ["visit", "extra-traits", "full"] }
+syn = { version = "2.0.42", features = ["visit", "extra-traits", "full"] }
 quote = "1.0"
 
 [[bench]]