Compatibility fix: delete_fragments

[kounelisagis]

In #1958 the static method delete_fragments replaced the instance method with the same name. This, instead of deprecation warning, caused errors for vector search tests: https://github.com/TileDB-Inc/TileDB-Vector-Search/actions/runs/9060651237/job/24890783433?pr=369

In this PR:

• Since both methods have the same name and number of required arguments, it's impossible to have two separate methods in Python even after using the @staticmethod decorator. We use just one function, checking the argument type.
  Both tiledb.Array.delete_fragments(path, 2, 2) and

>>> with tiledb.open(path, 'm') as A:
...     A.delete_fragments(2, 2)

are now valid.

• A higher level delete_fragments() function is deleted. Should have been removed since 0.21.0.

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[sc-47282]