gh-92886: Remove assert in clinic.permute_optional_groups so that it works when running with optimizations

[jackh-ncl]

Replacing assert statement with raise AssertionError(). This also fixes a test in test_clinic.py which fails when ran with -O.

#92886

Before:

$ ./python.exe -Om unittest test.test_clinic
.....F.................................................
======================================================================
FAIL: test_have_left_options_but_required_is_empty (test.test_clinic.ClinicGroupPermuterTest.test_have_left_options_but_required_is_empty)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/.../dev/cpython/Lib/test/test_clinic.py", line 156, in test_have_left_options_but_required_is_empty
    self.assertRaises(AssertionError, fn)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: AssertionError not raised by fn

----------------------------------------------------------------------
Ran 55 tests in 0.098s

FAILED (failures=1)

After:

./python.exe -Om unittest test.test_clinic
.......................................................
----------------------------------------------------------------------
Ran 55 tests in 0.098s

OK

[bedevere-bot]

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[iritkatriel]

Sorry this was done in another PR.