Updated mediawiki/extensions
Project: mediawiki/extensions/Flow  c618bc4c9de255631e0d4906f8e2ce8be1c79b9b

Kill previewButton helper

It's a silly use of a helper. Let's simplify the template and associate
the template needed for previews with the textarea it is doing a preview of.

Change-Id: Iac0875e28af0b6afcc9c6a898f018df00352a104