Fixed obvious unreferenced bug in copy-and-cast logic

[oleksandr-pavlyk]

The special casing of copy-and-cast operation after stride simplification, the branch where memcpy is applicable did not set returned event to the intended variable, but rather to the local-scoped one.

This change fixes that logic.

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[github-actions]

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

[coveralls]

coverage: 87.883%. remained the same
when pulling 79dc399 on fix-unreference-bug-in-copying-between-usm-ndarrays
into 76b2eb0 on master.

[github-actions]

Array API standard conformance tests for dpctl=0.18.0dev0=py310ha798474_307 ran successfully.
Passed: 894
Failed: 1
Skipped: 119