The prayer was suppressed in 1930. (Just in time for the Nazis.)
http://spellsandmagic.com/Shrine2Michael.html
It wasn’t surpressed then. It was omitted in the 1962 edition of the Roman Missal, though most places that offer the TLM still say it after the Low Mass. The oldest Catholic parish in Virginia, St. Mary’s in Alexandria, the prayer is recited after every single Mass.