Updated mediawiki/extensions
Project: mediawiki/extensions/VectorBeta  7e2f2a88bade65f83de39e290ada6b2754c5ff0e

Add Fixed header experiment to Vector Beta

Winter. It's on.
$wgVectorBetaWinter = true to enable.

Change-Id: I8f34fdbc4857adb8534bc9393749ba2bf5ca37fc