Bump proptest from 1.3.1 to 1.4.0 (#3198)

* Bump proptest from 1.3.1 to 1.4.0

Bumps [proptest](https://github.com/proptest-rs/proptest) from 1.3.1 to 1.4.0.
- [Release notes](https://github.com/proptest-rs/proptest/releases)
- [Changelog](https://github.com/proptest-rs/proptest/blob/master/CHANGELOG.md)
- [Commits](https://github.com/proptest-rs/proptest/compare/v1.3.1...v1.4.0)

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

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

* Update MSRV to 1.65 to match proptest

Rust 1.65 is just over one year old right now.

---------

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

.github/workflows/rust-tests.yml

@@ -15,7 +15,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - "1.64" # MSRV
+          - "1.65" # MSRV
           - "stable"
         os:
           - ubuntu-latest