Im not sure, but someone said in a previous thread that if you put a bit of griptape on your brake, bomb a hill and uuse your brake softly, it will get rid of it.
I dunno whether that griptape thing works . Cause once I was playing scoot with a guy who like loves tyre taps, like absolutely loves them... So I put grip tape on the footside of my brake, and it heated up and just fell off... I dunno if it would be the same on the other side but yeah....
first get some heavy grit sand paper
then take your wheel and try to round the flat spot out as much as you can
then dedicate a day to riding alot with that wheel and it should come out..