mw.ViewPageTarget.init: Only bind edit section links on view page

The handler for the Edit tab already is in this conditional,
for edit section we were making the assumption that they only
ever appear on a view page, but that's wrong. They're also shown
on a diff against the latest revision of the page.

Bug: 50925
Change-Id: I802e548cbcdc03cfca66129466668854604bc3e7
Merge "mw.ViewPageTarget.init: Only bind edit section links on view page"