Fix documentation warning when rendering `diff` docstring

[ndgrigorian]

This PR fixes a warning caused by the docstring for diff incorrectly indenting the description of the output shape.

Closes #1849

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[github-actions[bot]]

Deleted rendered PR docs from intelpython.github.com/dpctl, latest should be updated shortly. :crossed_fingers:

[github-actions[bot]]

Array API standard conformance tests for dpctl=0.19.0dev0=py310hdf72452_109 ran successfully. Passed: 895 Failed: 0 Skipped: 119

[github-actions[bot]]

Array API standard conformance tests for dpctl=0.19.0dev0=py310hdf72452_110 ran successfully. Passed: 895 Failed: 0 Skipped: 119

[coveralls]

coverage: 87.907%. remained the same when pulling 82706e8d9a7e1f0f9bdac02fe02fa9667d472178 on fix-diff-docstring into 7ae2a91628136969d331b09a6497767f680b6132 on master.

[oleksandr-pavlyk]

The reported sphinx errors are gone indeed. One outstanding issue is

/home/runner/work/dpctl/dpctl/dpctl/tensor/_indexing_functions.py:docstring of dpctl.tensor._indexing_functions.take_along_axis:24: WARNING: undefined label: 'broadcasting'

[oleksandr-pavlyk]

@ndgrigorian Could you please rebase your branch to pick up fix for the CI?

[ndgrigorian]

@ndgrigorian Could you please rebase your branch to pick up fix for the CI?

It's been rebased

[github-actions[bot]]

Array API standard conformance tests for dpctl=0.19.0dev0=py310hdf72452_114 ran successfully. Passed: 894 Failed: 1 Skipped: 119