Remove mitigation for keys leaking into the main window

[Zolixguru]

First of all, very good extension!

Issue:

• a mail to move selected,
• mouse click on Quick Move button up there (or Ctrl-Shift-N - it works now well) - the Quick Move dialog displayed,
• but if (accidently or not) the mouse cursor is moved over the list of last used folders below, the search field is deactivating, and we have to click on the search field to be able to type the searched characters (string),
• ! and if typed without clicking on search field, Thunderbird executes the commands associated with typed characters,
• so when we move the mouse accidently, we may not realize at first, that we are not pressing the keyboard keys for/to the search field but for example we're running 'a'-command to archive the mail.
  It was happening to me many times, it could be really confusing, because a couple of key presses do something in Thunderbird(I like these functions by the way).

So the solution could be to not deactivating the search field until a click is happening on some folder name below.

Thanks

[kewisch]

I have a mitigation in 5793575 for this, but it is actually a Thunderbird bug. I've filed https://bugzilla.mozilla.org/show_bug.cgi?id=1859023

I'll leave this issue open with a different title to adjust after the upstream issue is fixed.