Removes manual deep copy of memory objects in Crew.copy().
The Pydantic model_validator 'create_crew_memory' handles the
initialization of new memory instances for the copied crew.
Updates test_crew_copy_with_memory assertions to verify that
the private memory attributes (_short_term_memory, etc.) are
correctly initialized as new instances in the copied crew.
Co-Authored-By: Joe Moura <joao@crewai.com>
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