Changing multiple spaces to tabs for indentation

As per MediaWiki's coding conventions (https://www.mediawiki.org/wiki/Manual:Coding_conventions), all indentation done in PHP files should be done using tabs as opposed to single or multiple spaces.

Whether or not this file/extension is used in Wikia anymore, it should still follow MediaWiki's coding conventions.

No functional changes in this commit.
Merge pull request #2962 from georgebarnick/patch-2

Changing multiple spaces to tabs for indentation