chore: add classifiers for python 3.9 and python 3.10 (#211)

added support for python 3.9 and 3.10

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Fixes #212 🦕

packages/google-cloud-kms/setup.py

@@ -71,6 +71,8 @@
  "Programming Language :: Python :: 3.6",
  "Programming Language :: Python :: 3.7",
  "Programming Language :: Python :: 3.8",
+ "Programming Language :: Python :: 3.9",
+ "Programming Language :: Python :: 3.10",
  "Operating System :: OS Independent",
  "Topic :: Internet",
  ],