Debounce Mousetrap when navigating discussions

Potential solution

The following discussion from gitlab-ce!30144 should be addressed:

• @pslaughter started a discussion:

  issue: This is definitely not a blocker, but is there anyway we could debounce our Mousetrap handler? Things get a little funky if you just keep hitting "n" as fast as you can.

  But Paul, what do you mean "funky"?

  It seems like the calls stack so it keeps bouncing until the last "n" has been dealt with.