Fix ValueError testcases of `random.choice`
Fix ValueError testcases of `random.choice`

The assertion in the previous test didn't work as intended.
Applying `cupy.asarray` to a ragged nested sequence results raises
`ValueError: Unsupported dtype object`, while `numpy.asarray` constructs
an object-array (with VisibleDeprecationWarning) in NumPy.

This commit replaces the testcases with pure `ndim` checks:
- `ValueError: a must be 1-dimensional`
- `ValueError: p must be 1-dimensional`

cupy/cupy,cupy/cupy,cupy/cupy,cupy/cupy