Prevent double encoding of post content in history/rc

This bit of code is requesting the html version of the content and
using strip_tags to get a text representation.  This does not need
htmlspecialchar's since the text content is already HTML encoded.

Change-Id: I10b123a0eaaf9d5745ed63cb31366b49a9b2a543
Merge "Prevent double encoding of post content in history/rc" into frontend-rewrite