Revert "Add new recentchanges field rc_source to replace rc_type"

Apparently the rc_source column has been added on only 158 out of 879 wikis total.

Needs to be merged and deployed before/at the start of todays deploy

This reverts commit 6bbd4bca6c1341395988fdfdcf4788ce187edfa9.

Change-Id: Ibcf77ed7f04c14a477d7cfd0e244929c552c3394
(cherry picked from commit 189b7364b5e48d86ec0b078c8aad7124e4d09b29)