shorten the deprecation messages for clone() and copyWith()

protoc_plugin/CHANGELOG.md

@@ -4,6 +4,8 @@
 * Read `default_host` and `oauth_scopes` options from gRPC service definitions
   and write that information to the generated gRPC clients.
 * Generate dartdocs for grpc services ([#973]).
+* Adjust the deprecation messages for the message `clone()` and `copyWith()`
+  methods ([#998]).
 
 We now parse and generate code cooresponding to the proto options
 `google.api.default_host` and `google.api.oauth_scopes`:
@@ -49,6 +51,7 @@ class FirestoreClient extends $grpc.Client {
 [#975]: https://github.com/google/protobuf.dart/issues/975
 [#952]: https://github.com/google/protobuf.dart/issues/952
 [#986]: https://github.com/google/protobuf.dart/issues/986
+[#998]: https://github.com/google/protobuf.dart/issues/998
 
 ## 22.0.1