Update grpc versioning to make point clearer (#33680)

Co-authored-by: Wade Pickett <wpickett@microsoft.com>

aspnetcore/grpc/versioning.md

@@ -35,7 +35,7 @@ These changes are non-breaking at a gRPC protocol level and .NET binary level.
 * **Adding a new service**
 * **Adding a new method to a service**
 * **Adding a field to a request message** - Fields added to a request message are deserialized with the [default value](https://developers.google.com/protocol-buffers/docs/proto3#default) on the server when not set. To be a non-breaking change, the service must succeed when the new field isn't set by older clients.
-* **Adding a field to a response message** - Fields added to a response message are deserialized into the message's [unknown fields](https://developers.google.com/protocol-buffers/docs/proto3#unknowns) collection on the client.
+* **Adding a field to a response message** - If an older client hasn't been updated with the new field, the value is deserialized into the response message's [unknown fields](https://developers.google.com/protocol-buffers/docs/proto3#unknowns) collection.
 * **Adding a value to an enum** - Enums are serialized as a numeric value. New enum values are deserialized on the client to the enum value without an enum name. To be a non-breaking change, older clients must run correctly when receiving the new enum value.
 
 ### Binary breaking changes