Remove duplicate get_integer_from_var_name tests from memcpy_hint_utils

[Galoretka]

Description

• Removed misplaced duplicate tests in vm/src/hint_processor/builtin_hint_processor/memcpy_hint_utils.rs that asserted get_integer_from_var_name() behavior.
• These tests belong to hint_utils.rs and already exist there; keeping duplicates is redundant.
• Functions in memcpy_hint_utils.rs remain covered by existing tests in builtin_hint_processor_definition.rs and utils.rs

Checklist

• Linked to Github Issue
• Unit tests added
• Integration tests added.
• This change requires new documentation.
  • Documentation has been added/updated.
  • CHANGELOG has been updated.