Why does 'turn on dictation' pop up when pressing D key on MacBook Air 2019?

I have a MacBook Air 2019, when I press the D key while I’m playing video games the “turn on dictation” pops up. I’ve gone through my settings I completely turned it off even the shortcut is set to off, but I still get the pop up when I press the D key. 

[Re-Titled by Moderator]