fix: pytype client errors

[rafilong]

Adds pytype to gitignore and fixes the following:

[47/63] check base_client
FAILED: /home/rafilong/workspace/googleapis/python-firestore/.pytype/pyi/base_client.pyi 
/home/rafilong/workspace/googleapis/python-firestore/.nox/pytype/bin/python -m pytype.single --disable pyi-error --imports_info /home/rafilong/workspace/googleapis/python-firestore/.pytype/imports/base_client.imports --module-name base_client -V 3.8 -o /home/rafilong/workspace/googleapis/python-firestore/.pytype/pyi/base_client.pyi --analyze-annotated --nofail --quick /home/rafilong/workspace/googleapis/python-firestore/google/cloud/firestore_v1/__pycache__/base_client.py
File "/home/rafilong/workspace/googleapis/python-firestore/google/cloud/firestore_v1/__pycache__/base_client.py", line 37, in <module>: Can't find module 'google.cloud.firestore_v1.gapic'. [import-error]
File "/home/rafilong/workspace/googleapis/python-firestore/google/cloud/firestore_v1/__pycache__/base_client.py", line 38, in <module>: Can't find module 'google.cloud.firestore_v1.gapic.transports'. [import-error]