x11/dmenu: Patch an input focus bug

Dmenu 4.9 was release with a bug causing problems with input focus. We
apply a temporary fix while upstream prepares a new release.

Mailing list discussion: https://lists.suckless.org/dev/1902/33272.html

PR: 236107
Submitted by: Oleh Hushchenkov <o.hushchenkov@gmail.com>
Reviewed by: mat
Approved by: mat (mentor)
Differential Revision: https://reviews.freebsd.org/D19414