Revert "Overlay mms_config to increase allowed picture size"

This value is rejected by multiple carriers. 300K is a safe limit, 1MB isn't. 2 out of 3 carriers in my region reject messages due to this.

Please re-submit this overlayed for mcc/mnc pairs of carriers in which this is _known_ to be working.

This reverts commit 43543e4a2df9d7a3376cf6c7f44bb5cbf448f4aa.

Change-Id: I13a6aa5c2e314e7e07abcdb6f30b3e4170fb11b3