pin protobuf version (#40)

Author: saumil-d

setup.py

@@ -11,7 +11,7 @@
 with open('HISTORY.rst') as history_file:
     history = history_file.read()
 
-requirements = ['requests', 'python-dotenv', 'deprecation', 'protobuf', 'grpcio', 'google-api-python-client']
+requirements = ['requests', 'python-dotenv', 'deprecation', 'protobuf==3.19.4', 'grpcio', 'google-api-python-client']
 
 # removed in 0.7.1 test_requirements = ['pytest']