Fixed too wide selector for the popovermenu

[skjnldsv]

This was interfering with some other menus on the nextcloud server

@nextcloud/javascript @nextcloud/designers

[skjnldsv]

Test failure not related to this pr. Master is broken apparently! https://travis-ci.org/nextcloud/gallery/builds

[blizzz]

gnah, within vendor/, no wonder ack didn't find that occurence when i was looking for "icon-more"

[skjnldsv]

@blizzz same, my grep exclude was messing with me! 😉