Removing backwards-compatibility CSS from an earlier change. Follow-up to Idf43d77dccff83ad81db776f3262e0ef12d25c92. Change-Id: I2817c6e9eb52ffc785a04bb9d23b0802a553fd45
This is the final step of the process described at <https://www.mediawiki.org/wiki/Separating_skins_from_core_MediaWiki>. Corresponding core change: Idfc38503. Change-Id: I84fcf7ce6385b8323544cafe6912a00f1886d20d