Loosen Typing Extensions Requirement

The current beam python package requirements are very strict for typing extensions package here. The requirement only allows 3.7 and doesn't allow minor updates like 3.8 or current 3.10. The typing extensions package is pretty stable and is mainly used to add new type hint features from recent peps. As the changes are almost all additive it should be safe to have looser requirement and at least be just >3.7. The current tight restrictions means using beam as a library blocks me from using newer type hint features. Could we loosen the requirement?

I've made a small pull request for it here, https://github.com/apache/beam/pull/15233.