Sidebar tabs design update

[marcoambrosini]

• Remove border
• Ellipse text instead of 2 lines

As discussed with @jancborchardt

[dartcafe]

Does it address this "feature"?

[marcoambrosini]

So I've been a bit reluctant with this because I think our current system doesn't work and we need to think this through a bit more. I think that we need to take a step back here and rethink how we do the sidebar altogether. I'm closing for now as this is just a cosmetic change that is not solving problems and in fact ellipsizing text on buttons is something that we've come to normalise but is just unacceptable.

[jancborchardt]

The ideal case would be that we just have 3 sidebar tabs:

• Activity: All chronological info
• Sharing
• Details

Also ref nextcloud/server#658

And this issue here is precisely about the visual part, which should be fixed as well, not closed.
@marcoambrosini Stepping back to think about a perfect solution doesn't mean we have to leave the current state unwell. We need to work step by step on improving.

[marcoambrosini]

I thought I was the only one that disliked the border so I figured I should leave it there as it doesn't really solve much. Implemented now.
Label trimming is already in.