build(deps): update syn requirement from 1.0 to 2.0
Updates the requirements on [syn](https://github.com/dtolnay/syn) to permit the latest version.
- [Release notes](https://github.com/dtolnay/syn/releases)
- [Commits](https://github.com/dtolnay/syn/compare/1.0.0...2.0.3)
---
updated-dependencies:
- dependency-name: syn
dependency-type: direct:production
...
Signed-off-by: dependabot[bot] <[email protected]>