Update Danger Database rules to exclude development fixtures
Problem to solve
Danger's database configuration currently checks the entirety of
/db to ensure proper review by the database team. We should exclude
db/fixtures/development from the
db_paths_to_review as it should not necessary for the database team to review changes to development fixtures.
Update [Danger database configuration](https://gitlab.com/gitlab-org/gitlab-ce/blob/v11.8.0-rc1/danger/database/Dangerfile] to exclude
db/fixtures/development/**/* from requiring review