Fix DECRPM parsing for 2026
Fix DECRPM parsing for 2026

As discovered in #4320 the previous code was buggy and would enable
synchronized output on any response.

casimir/kakoune,casimir/kakoune,mawww/kakoune,mawww/kakoune,mawww/kakoune,mawww/kakoune,casimir/kakoune,jkonecny12/kakoune,jkonecny12/kakoune,jkonecny12/kakoune,casimir/kakoune,jkonecny12/kakoune