Resolve a typo in exceptions docstrings

[antonwolfy]

This PR updates text in SyclContextCreationError and SyclDeviceCreationError exception to fix a typo there.
Also minor typos in a test and example were resolved.

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[vlad-perevezentsev]

LGTM
Thank you @antonwolfy

[github-actions]

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

[github-actions]

Array API standard conformance tests for dpctl=0.21.0=py310h93fe807_24 ran successfully.
Passed: 1115
Failed: 6
Skipped: 119

[coveralls]

coverage: 85.264%. remained the same
when pulling 516acaa on fix-typo-in-exceptions-docstrings
into 3dfc117 on master.