Delete custom test file again

We'll set up a proper testing architecture after the
migration to cirrus is complete

moor/dart_test.yaml

@@ -1,11 +0,0 @@
-# https://github.com/dart-lang/test/blob/master/pkgs/test/doc/configuration.md#configuring-tags
-
-platforms:
-  - vm
-#  - firefox
-#  - chrome
-
-override_platforms:
-  firefox:
-    settings:
-      arguments: -headless