fix(deps): allow protobuf 3.19.5 (#577)

Author: parthea

packages/pandas-gbq/testing/constraints-3.7.txt

@@ -16,4 +16,4 @@ pandas==0.24.2
 pyarrow==3.0.0
 pydata-google-auth==0.1.2
 tqdm==4.23.0
-protobuf==3.20.2
+protobuf==3.19.5