Braxton didn't undo Adm. Janeway's bringing Voyager home early.
How can we be sure? Apart from Nemesis - which completely ignores Voyager (and pretty much everything else) - that was the last scene we ever saw from the 24th century! For all we know, Braxton could have changed everything back and the Voyager crew is still out there in the DQ!
Um, Admiral Janeway?