Bump betterproto from 2.0.0b5 to 2.0.0b6

Bumps [betterproto](https://github.com/danielgtaylor/python-betterproto) from 2.0.0b5 to 2.0.0b6.
- [Release notes](https://github.com/danielgtaylor/python-betterproto/releases)
- [Changelog](https://github.com/danielgtaylor/python-betterproto/blob/master/CHANGELOG.md)
- [Commits](danielgtaylor/python-betterproto@v2.0.0b5...v.2.0.0b6)

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

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

Author: dependabot[bot]

requirements.txt

@@ -1,4 +1,4 @@
-betterproto==2.0.0b5
+betterproto==2.0.0b6
 hagelkorn
 numpy
 pandas