Change "max dimensions" to None in array API capabilities

[ndgrigorian]

tensor.usm_ndarray can support potentially arbitrary dimensions

Changes will need to be made where NumPy arrays are created from usm_ndarray (printing, dlpack with kDLCPU, asnumpy/from_numpy)

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[github-actions]

View rendered docs @ https://intelpython.github.io/dpctl/pulls/2071/index.html

[coveralls]

coverage: 86.363%. remained the same
when pulling a6500fa on unrestrict-max-dimensions
into 32948cd on master.

[github-actions]

Array API standard conformance tests for dpctl=0.20.0dev0=py310h93fe807_179 ran successfully.
Passed: 1109
Failed: 3
Skipped: 119