That's normal wear. The flat spot's width represents the width of the contact patch when you're riding straight. The tire deflects from round to flat where it meets the pavement, and that's how they wear.
The only way to get rid of it is to ride twisty mountain roads on a regular basis. That'll have the bike banked to either side more of the time, and keep the crown round.
Otherwise, stop looking so close, and ride the bike.
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