Minor code cleanup: Remove some unneeded imports, etc.

project.clj

...ntend_client/app/admin/databases/databases.controllers.js

...nd_client/app/admin/databases/partials/database_list.html

...es/frontend_client/app/components/form/FormLabel.react.js

resources/frontend_client/app/metabase/metabase.services.js

resources/migrations/017_add_database_is_sample_field.yaml

resources/migrations/liquibase.json

src/metabase/api/database.clj

src/metabase/core.clj

src/metabase/db/migrations.clj

src/metabase/driver/mongo/util.clj

src/metabase/events.clj

src/metabase/events/activity_feed.clj

src/metabase/events/last_login.clj

src/metabase/sample_data.clj

src/metabase/task.clj

src/metabase/task/sync_databases.clj

test/metabase/api/database_test.clj

test/metabase/api/field_test.clj

test/metabase/api/table_test.clj