**Backport:** https://codeberg.org/forgejo/forgejo/pulls/4551
This aligns the popup width of the label selector during issue creation
to the width of the label selector in an already created issue.
(The inherited width from "ui form" is reset to prevent width: 100% on the
input element in the search box.)
This is a follow-up to https://codeberg.org/forgejo/forgejo/pulls/4546
(cherry picked from commit b32a03531c)
