Turn _s to spaces in highlighted namespaces

It turns out that getNsText spits out _s.  Title->getPrefixedText deals
with this but we can't use it because we have different text.  So we must
replace the _s ourselves.

Bug: 60298
Change-Id: I93bedd780a6e492f25d7c788eb640830718f47e2
Merge "Turn _s to spaces in highlighted namespaces"