api: stabilize ServerCall.getAuthority() by removing experimental annotation (grpc#10498)

Author: sanjaypujare

api/src/main/java/io/grpc/ServerCall.java

@@ -242,7 +242,6 @@ public Attributes getAttributes() {
    *
    * @return the authority string. {@code null} if not available.
    */
-  @ExperimentalApi("https://github.com/grpc/grpc-java/issues/2924")
   @Nullable
   public String getAuthority() {
     return null;