Don't run progressiveEnhancements through handlebars.js

{{Foo}} in the topic title is treated as a handlebars template in topic
reply placeholder.  I looked over the other uses of progressiveEnhancement
and it didn't appear there were any current uses of this functionality.
So i removed it.

Bug: 70982
Change-Id: I320e18de511de5462492bf6bf2f0161530087f7b
(cherry picked from commit 8b7bfaf16463085b94818f946760f6f39c4abd9b)
Merge "Don't run progressiveEnhancements through handlebars.js" into wmf/1.24wmf22