build(deps): bump proptest from 1.5.0 to 1.6.0 (#7)

Bumps [proptest](https://github.com/proptest-rs/proptest) from 1.5.0 to 1.6.0.
- [Release notes](https://github.com/proptest-rs/proptest/releases)
- [Changelog](https://github.com/proptest-rs/proptest/blob/main/CHANGELOG.md)
- [Commits](https://github.com/proptest-rs/proptest/commits)

---
updated-dependencies:
- dependency-name: proptest
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

program/Cargo.toml

@@ -33,7 +33,7 @@ bincode = "1.3.1"
 
 [dev-dependencies]
 assert_matches = "1.5.0"
-proptest = "1.5"
+proptest = "1.6"
 solana-program-test = "2.1.0"
 solana-sdk = "2.1.0"
 solana-vote-program = "2.1.0"