Changed keydown listener in removeListeners()

[stefanreimers]

addEventListener -> removeEventListener

[msftclas]

Hi @stefanreimers, I'm your friendly neighborhood Microsoft Pull Request Bot (You can call me MSBOT). Thanks for your contribution!

This seems like a small (but important) contribution, so no Contribution License Agreement is required at this point. Real humans will now evaluate your PR.

TTYL, MSBOT;

[Jahnp]

Approved

Thanks for catching & fixing this, @stefanreimers!

[mikewheaton]

Approved