Hi,

I was not sure how to send a pull request to fix an earlier version of google-api-core that's not being developed anymore, but newer version of protobuf breaks the support for python 2.

This is for release-v1.32.0, or the last version that supported python 2.7.

We only need to modify the condition here : https://github.com/googleapis/python-api-core/blob/main/setup.py#L33
"protobuf >= 3.12.0, < 3.18.0",