refactor(heap): remove redundant TypeVar in Heap

[iosayin]

Describe your change

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
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Removes redundant TypeVar import and definition in data_structures/heap/heap.py, relying on Python 3.12+ PEP 695 generic class parameter syntax class Heap[T: Comparable]:. Also aligns Comparable.__gt__ signature with standard Protocol style.

Reference: #15234

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[cclauss]

Please revert this change. We want both self and other to be of type T.

[iosayin]

Reverted the Comparable.__gt__ signature back to self: T, other: T as requested. Thanks!