DOC: Clarify docs on mixed advanced indexing and slicing (gh-15891)
DOC: Clarify docs on mixed advanced indexing and slicing (gh-15891)

It was not clear how to reproduce the slice example with multi dimensional array indexing. I hope the additional example clarifies the equivalence between slice and multi array for new users.

Co-Authored-By: Eric Wieser <da64e90baec5d084ce3d8e05f3b022ae6d118ff5@gmail.com>
Co-Authored-By: Anirudh Subramanian <1f2242ce057dd4b668ef3d07f2b806138e4c20bf@apache.org>
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