mediawiki: get rid of envvars files in puppet.

After restoring the vanilla envvars from ubuntu, we can just plainly
remove them from the repository and just leave the defs we need.

Change-Id: Ie7897d8b916a3a726a2b4ca7943ab3df5f1ca86e
Signed-off-by: Giuseppe Lavagetto <glavagetto@wikimedia.org>