chore(deps): update dependency protobuf to v6

This MR contains the following updates:

Package	Update	Change
protobuf	major	==4.25.0 -> ==6.30.1

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cloud-function/requirements.txt

@@ -30,7 +30,7 @@ httplib2==0.22.0
     #   google-auth-httplib2
 idna==3.4
     # via requests
-protobuf==4.25.0
+protobuf==6.30.1
     # via
     #   google-api-core
     #   googleapis-common-protos