mediawiki: syntax typo fix, remove unused modules

A few modules get loaded by default in debian's apache, but we do not
use them in the original config we had, so it's safer (and more memory
conscious) to remove them for now and reenable just the ones we need or
think are useful later on.

Change-Id: Idc1e4dbf002443cd7966bbbb9010ae8dd941c37c
Signed-off-by: Giuseppe Lavagetto <glavagetto@wikimedia.org>