Don't escape HTML title of Special:Contributions for newbies

This is a correction regarding the call of "->plain".
MediaWiki:pagetitle may contain variables (such as {{SITENAME}})
to be parsed, so it should not be treated as plain text.
MediaWiki:sp-contributions-newbies-title appears to be plain text only.

Change-Id: Ia6c0d955fb789535104956be9a00ce432aabe9e1
Merge "Don't escape HTML title of Special:Contributions for newbies"