The current layout gave too little space for the full "Search" string inside the button. Fix this by making sure radio-buttons have their text center aligned by default in pop-ups too, like they do anywhere else. This does affect a few other cases, e.g. the "RGB"/"HSV"/"Hex" radio-toggles for color pickers. But this should be fine, I don't think they were ever intentionally using left-aligned text (while similar buttons outside of pop-ups didn't).