fix(views): show different text on widgetpanel toggle button when opened

fixes #4826 

TODOs:
 - [ ] Come to agreement on how to accomplish this without inline JS
no we can't as it is too low level. Anchors like these (and in most other menus) get `.elgg-menu-hz > li > a` which adds `display: inline-block` and thus overrules hidden attribute. Class `hidden` wins!