Bump propcache from 0.2.0 to 0.2.1

Bumps [propcache](https://github.com/aio-libs/propcache) from 0.2.0 to 0.2.1.
- [Release notes](https://github.com/aio-libs/propcache/releases)
- [Changelog](https://github.com/aio-libs/propcache/blob/master/CHANGES.rst)
- [Commits](aio-libs/propcache@v0.2.0...v0.2.1)

---
updated-dependencies:
- dependency-name: propcache
  dependency-type: indirect
  update-type: version-update:semver-patch
...

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