faq.md: Include note that renaming the package name breaks gRPC

The gRPC protocol includes the fully-qualified protobuf names for the request/response types, so renaming the package breaks this. Add a note about this.

Author: evanj

content/reference/go/faq.md

@@ -152,9 +152,9 @@ Common ways that namespace conflicts occur:
     deliberately chosen to be universally unique (for example, prefixed with the
     name of a company).
 
-    *   Warning: Retroactively changing the package name on a `.proto` file can
-        potentially cause the use of extension fields or messages stored in
-        `google.protobuf.Any` to stop working properly.
+    *   Warning: Retroactively changing the package name on a `.proto` file is
+        not backwards compatible for types used as extension fields, stored in
+        `google.protobuf.Any`, or used as gRPC requests or responses.
 
 Starting with v1.26.0 of the `google.golang.org/protobuf` module, a hard error
 will be reported when a Go program starts up that has multiple conflicting