Remove now redundant code

MessageFormatter and FormattingTuple were originally
copied from Netty because they didn't have the proper
access modifiers for us to use them.
With Netty 4.1.81 now being used in Quarkus, we can now
use the actual classes so let's get rid of the redundancy.

Follows up on: quarkusio#27653, quarkusio#28077