Remove passive_deletes warning for many-to-one

Remove passive_deletes warning for many-to-one

Removed very old warning that states that passive_deletes is not intended
for many-to-one relationships. While it is likely that in many cases
placing this parameter on a many-to-one relationship is not what was
intended, there are use cases where delete cascade may want to be
disallowed following from such a relationship.

Change-Id: I07adb726633f73f26296add4ec70376d5dcf8817
References: #5983