match gps_a to _gps_a
match gps_a to _gps_a

Co-authored-by: Paul La Plante <66d238e4e48f8b5ed8fbf0588af7b10437d552c9@berkeley.edu>
HERA-Team/pyuvdata,HERA-Team/pyuvdata,HERA-Team/pyuvdata,HERA-Team/pyuvdata