chore: remove dependency on google-api-core (#1372)

* chore(deps): update dependency google-api-core to v2.7.1

* chore: remove dependency on google-api-core

Co-authored-by: Anthonios Partheniou <partheniou@google.com>

requirements.txt

@@ -8,12 +8,6 @@ deprecation
 protobuf==3.19.3
 watchdog
 
-# https://github.com/googleapis/gapic-generator/issues/3334
-# temporarily install google-api-core for gapic-generator-python
-# Bazel should install this, but there is currently a bug
-# that causes the package to be skipped
-google-api-core==2.0.0
-
 # some java processing requires xml handling
 lxml