Do not pin grpc dependencies #199

Job	Run time
Test with nox (ubuntu-20.04, 3.11, pytest_min)	32s
Check proto files with protolint	10s
Test with nox (ubuntu-20.04, 3.11, ci_checks_max)	49s
Test documentation website generation	32s
Build distribution packages	25s
Cross-arch tests with nox	0s
Cross-arch tests with nox	0s
Test package installation in different architectures	1m 44s
Test with nox	2s
Publish documentation website to GitHub pages	0s
Publish packages to PyPI	0s
Create GitHub release	0s
	4m 14s

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