Correct ImageOps.crop border type hint

[lllleolin-max]

ImageOps.crop(im, (1, 2)) and ImageOps.crop(im, (1, 2, 3, 4)) already work through _border(), but type checkers reject them because crop() only annotates border as int.

Changes proposed in this pull request:

• Match the existing tuple support in the crop() annotation, consistent with expand().
• Document integer, horizontal/vertical and left/top/right/bottom border forms for both functions, replacing the inaccurate statement that crop() always removes the same border on every side.
• Add typed crop tests for all three forms.

Validation:

• With MYPYPATH=src, python3 -m mypy --follow-imports=silent --ignore-missing-imports Tests/test_imageops.py: the new test produces one arg-type error with the old annotation, and passes with the updated annotation.
• All 49 tests in Tests/test_imageops.py pass with the checkout's ImageOps module and Pillow 12.3.0's prebuilt native extensions on Windows/Python 3.12. The native extensions were not rebuilt.
• Black, Ruff, Sphinx-lint and git diff --check pass for the changed files.
• The full Sphinx HTML documentation builds successfully with warnings treated as errors, using the checkout's ImageOps module and Pillow 12.3.0 for the other modules.

Prepared with AI assistance.

[radarhere]

I've created lllleolin-max#1 with suggestions.