Dangerfile: Fix undefined method

What does this MR do?

Changes introduced in !40641 (merged) cause this error:

undefined method has_database_scoped_labels?
from danger/database/Dangerfile:62

This is happening to merge requests labeled with database

See examples of the DangerBot error:

• !41407 (comment 406982221)
• !41091 (comment 405978204)
• !39731 (comment 398042990)