Remove ul margin around ul.topic-collapser

By default, some margin (0.3em 0 0 1.6em) is added around:

    .mw-content-ltr ul, .mw-content-rtl .mw-content-ltr ul

We don't want this around the topic-collapser ul.
In RTL-view, this margin is not really a problem since the li's are floated to
the right & the margin is added left (so the margin will not have any visual
effect). In LTR, however, the li's are on the left, and this ul-margin pushes
them inward.

Change-Id: I0e628668ea7d4b48022c38588824841243592e60
Merge "Remove ul margin around ul.topic-collapser"