fix(deps): require protobuf<4.0.0 on v0 branch (#105)

Author: parthea

setup.py

@@ -29,8 +29,9 @@
     # Until this issue is closed
     # https://github.com/googleapis/google-cloud-python/issues/10566
     "google-api-core[grpc] >= 1.31.5, <3.0.0dev,!=2.0.*,!=2.1.*,!=2.2.*,!=2.3.0",
-    "proto-plus >= 1.15.0",
-    "packaging >= 14.3",
+    "proto-plus >= 1.15.0, <2.0.0dev",
+    "packaging >= 14.3, <22.0.0dev",
+    "protobuf<4.0.0dev",
     "google-cloud-source-context >= 0.1.0, < 1.0.0dev",
 ]