Do not build dpctl for Python 3.8

[oleksandr-pavlyk]

Closes gh-1295

Stop building conda packages of dpctl for Python 3.8

• Have you provided a meaningful PR description?
• Have you added a test, reproducer or referred to an issue with a reproducer?
• Have you tested your changes locally for CPU and GPU devices?
• Have you made sure that new changes do not introduce compiler warnings?
• Have you checked performance impact of proposed changes?
• If this PR is a work in progress, are you opening the PR as a draft?

[coveralls]

coverage: 85.636%. remained the same when pulling 6f22fa0 on drop-py-3.8 into 3cbb221 on master.

[github-actions]

Array API standard conformance tests for dpctl=0.14.6dev4=py310ha25a700_10 ran successfully.
Passed: 916
Failed: 84
Skipped: 119

[antonwolfy]

I've opened a PR in dpnp with similar changes. Thank you @oleksandr-pavlyk for driving that !

[github-actions]

View rendered docs @ https://intelpython.github.io/dpctl/pulls/1363/index.html

[github-actions]

Array API standard conformance tests for dpctl=0.14.6dev4=py310ha25a700_11 ran successfully.
Passed: 916
Failed: 84
Skipped: 119

[github-actions]

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