Remove another slow RecipientCSV test
Remove another slow RecipientCSV test

This test was checking for several things covered by other tests:

- "initial_rows" is covered by "test_get_annotated_rows"
- "initial_rows_with_errors" is covered by "test_get_rows_with_errors"
- "rows" is covered by "test_errors_when_too_many_rows" (and others)
- "has_errors" is covered by several tests

alphagov/notifications-utils