Remove cursor:pointer CSS from li element

This is my *groundbreaking* pull request to fix #7758

Originating from https://github.com/owncloud/core/commit/7474c907dc715e790145e4577306c9936f60fa1d#commitcomment-5608393

`cursor:pointer` should not be set as default for `li` elements because not all `li` elements are clickable. For example see Calendar -> Edit event -> Share. The users are listed and seem clickable because of the cursor but they are not.

CC @owncloud/designers @jancborchardt