The meaning of this notation is to indicate that you are to switch from the current key signature back to A major for the repetition (since the start of the repetition will not in general announce the key signature if it is not changed from before the beginning of the repetition).
If the start of the repeat is not actually in A major, this is a notation error. There is no proper notation for "repeat but in a different key". If that were desired it had to be spelled out explicitly, and it would be the kind of thing one does in a manuscript but never in a printed edition.
Printed editions need to cater for the "perfect sightreader" playing off material in a brainless manner. "Substitute an entirely different key signature and reinterpret all accidentals accordingly" is not in the skill set pianists spend decades on perfecting. So if you change the key for a repeated passage, you reprint it in the changed key.