Revert "Updating gerrit to 2.6-rc0-7-g6e5cc39"

We won't be deploying this build--wasn't actually put in apt repo.

This reverts commit 8a74770c690aac37cf44dfcf2f69dc17d136831c

Change-Id: I83ce8a555cf39b96939a0f1c5c310459c5332400