Bump betterproto from 2.0.0b3 to 2.0.0b4

Bumps [betterproto](https://github.com/danielgtaylor/python-betterproto) from 2.0.0b3 to 2.0.0b4.
- [Release notes](https://github.com/danielgtaylor/python-betterproto/releases)
- [Changelog](https://github.com/danielgtaylor/python-betterproto/blob/master/CHANGELOG.md)
- [Commits](danielgtaylor/python-betterproto@v2.0.0b3...v2.0.0b4)

---
updated-dependencies:
- dependency-name: betterproto
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

requirements.txt

@@ -1,4 +1,4 @@
-betterproto==2.0.0b3
+betterproto==2.0.0b4
 hagelkorn
 numpy<1.22.0
 pandas