build(deps): bump syn from 1.0.61 to 1.0.64 (#332)

Bumps [syn](https://github.com/dtolnay/syn) from 1.0.61 to 1.0.64.
- [Release notes](https://github.com/dtolnay/syn/releases)
- [Commits](dtolnay/syn@1.0.61...1.0.64)

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

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

Author: dependabot[bot]