fix(deps): require protobuf <4.0.0dev (#287)

Author: parthea

setup.py

@@ -45,7 +45,8 @@
     include_package_data=True,
     install_requires=(
         "google-api-core[grpc] >= 2.7.0, <3.0.0dev",
-        "proto-plus >= 1.19.7",
+        "proto-plus >= 1.19.7, <2.0.0dev",
+        "protobuf >= 3.19.0, <4.0.0dev",
         "dataclasses >= 0.6; python_version < '3.7'",
     ),
     python_requires=">=3.6",

testing/constraints-3.6.txt

@@ -8,3 +8,4 @@
 google-api-core==2.7.0
 proto-plus==1.19.7
 dataclasses==0.6.0
+protobuf==3.19.0