mypy checks fail with click==8.1.0

[parthea]

There is a typing issue with click==8.1.0 which is causing the mypy check to fail in the main branch and #1251. See build log here.

Run nox -s mypy
nox > Running session mypy
nox > Creating virtual environment (virtualenv) using python3.10 in .nox/mypy
nox > python -m pip install mypy 'types-protobuf<=3.19.[7](https://github.com/googleapis/gapic-generator-python/runs/5753213728?check_suite_focus=true#step:5:7)' types-PyYAML types-dataclasses
nox > python -m pip install .
nox > mypy gapic
gapic/cli/generate.py:71: error: <nothing> not callable
Found 1 error in 1 file (checked 36 source files)