fix(deps): pin 'google-{api,cloud}-core', 'google-auth' to allow 2.x versions (#97)

Expand pins on library dependencies in preparation for these dependencies taking a new major version. See googleapis/google-cloud-python#10566.

Author: busunkim96

setup.py

@@ -44,7 +44,10 @@
  platforms="Posix; MacOS X; Windows",
  include_package_data=True,
  install_requires=(
- "google-api-core >= 1.22.2, < 2.0.0dev",
+ # NOTE: Maintainers, please do not require google-api-core>=2.x.x
+ # Until this issue is closed
+ # https://github.com/googleapis/google-cloud-python/issues/10566
+ "google-api-core >= 1.22.2, <3.0.0dev",
  "proto-plus >= 1.4.0",
  "packaging >= 14.3",
  "grpc-google-iam-v1 >= 0.12.3, < 0.13.0dev",