core: Document grpc does not perform compression nego on client

core/src/main/java/io/grpc/CallOptions.java

@@ -105,6 +105,10 @@ public final class CallOptions {
   /**
    * Sets the compression to use for the call.  The compressor must be a valid name known in the
    * {@link CompressorRegistry}.
+   *
+   * <p>It is only safe to call this if the server supports the compression format chosen. There is
+   * no negotiation performed; if the server does not support the compression chosen, the call will
+   * fail.
    */
   @ExperimentalApi("https://github.com/grpc/grpc-java/issues/1704")
   public CallOptions withCompression(@Nullable String compressorName) {