MAINT: align test_dispatcher s390x targets with _umath_tests_mtargets

[cbouss]

This updates https://github.com/numpy/numpy/blob/main/numpy/core/tests/test_cpu_dispatcher.py#L12 targets matching what is set at https://github.com/numpy/numpy/blob/main/numpy/core/meson.build#L688 (i.e. adding VE and VXE).

This was discovered when testing an s390x build with optimization on.

[seiko2plus]

Thank you, this fix should resolves #24750

[charris]

@seiko2plus The #24814 backport failed a test on the travis s390x. Might be a problem with the test .

>       assert_equal(test["func"], "func" + highest_sfx)
E       AssertionError: 
E       Items are not equal:
E        ACTUAL: 'func'
E        DESIRED: 'func_VXE'