Revert "(Bug 44394) Set $wgGrownUpBehavior to 'false'"

This reverts commit f3605b4f0a1245c27f4de1999d0969e871f99b02.

Change-Id: Ia7080f92ad00a4df2c1e12ffff21bb5263cfd517
Merge "Revert "(Bug 44394) Set $wgGrownUpBehavior to 'false'""