GHA: Remove obsolete code for old PyPy

[nulano]

Missed this as part of #4964.

• Revert Fix TCL in Windows PyPy tests #4702 now that the fix is released in PyPy 7.3.2.

The tests now pass without the workaround:
https://github.com/python-pillow/Pillow/pull/4984/checks?check_run_id=1262633517#step:27:1628

Tests/test_imagetk.py::test_kw PASSED                                    [ 94%]
Tests/test_imagetk.py::test_photoimage PASSED                            [ 94%]
Tests/test_imagetk.py::test_photoimage_blank PASSED                      [ 94%]
Tests/test_imagetk.py::test_bitmapimage PASSED                           [ 94%]

[nulano]

Travis finally finished after 4 hours! but Mergify can't actually merge this:

GitHub App like Mergify are not allowed to merge pull request where .github/workflows is changed.

[hugovk]

Ah yes. Thanks!