MR widget "tree" lines have issues on mobile.

Resources

FE: @psimyn

Here's a screen shot of a MR widget on an iPhone 6S screen. There are a couple of UI polish issues here.

From top to bottom:

1. The "Requires 0 more approvals" ought to be left-aligned so that the line below it appears to be attached to this heading (like the "Merged by ..." line below it)

2. The line next to the "The source branch has been removed" text is not vertically centered and appears to have a gap between where the vertical line ends and the horizontal line begins.

3. The "Issue XXX is mentioned but will not be closed." line has an excessively long vertical line, probably due to the text spanning multiple rows.