Defer on digital attestations for now

[daneah]

This change is a: (check at least one)

• Bugfix
• Feature addition
• Code style update
• Refactor
• Release activity

Is this a breaking change? (check one)

• Yes
• No

Is the:

• Title of this pull request clear, concise, and indicative of the issue number it addresses, if any?
• Test suite passing?
• Code coverage maximal?
• Changelog up to date?

What does this change address?

Attestations are preventing publishing. From the publishing action docs:

Support for generating and uploading digital attestations is currently experimental and limited only to Trusted Publishing flows using PyPI or TestPyPI. Support for this feature is not yet stable; the settings and behavior described below may change without prior notice.

How does this change work?

Disable attestations for now.