dev/ci: set go, database diff in backend integration runtype
Created by: bobheadxi
Run backend-integration/ branches with Go and DatabaseSchema diffs by default, since it makes sense in the context of wanting to run backend changes.
See https://sourcegraph.slack.com/archives/C01N83PS4TU/p1647642900757389
Test plan
sg ci build backend-integration
: https://buildkite.com/sourcegraph/sourcegraph/builds/137974