JS Components: fix weird spinner visual issue

[retrofox]

This PR fixes a visual issue in the Spinner components that happen for WordPress version < 6.0. Basically. The new spinner design from WordPress/gutenberg#37551 will be in WP 6.0 but isn't in 5.9 (thanks to @anomiex)

Fixes JS Components: fix weird spinner visual issue for WordPress < 6.0

Changes proposed in this Pull Request:

Jetpack product discussion

Does this pull request change what data or activity we track or use?

Testing instructions:

• Go to Protect plugin
• Disconnect the site
• Testi with WP < 6.0

before	after

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• To see the specific tasks where the Asana app for GitHub is being used, see below:
  • https://app.asana.com/0/0/1202204855890091
  • https://app.asana.com/0/0/1202203997123736

[matticbot]

Caution: This PR has changes that must be merged to WordPress.com
Hello retrofox! These changes need to be synced to WordPress.com - If you 're an a11n, please commandeer and confirm D79872-code works as expected before merging this PR. Once this PR is merged, please commit the changes to WP.com. Thank you!
This revision will be updated with each commit to this PR

[github-actions]

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[leogermani]

Works well for me.

The spinner has the right shape with Gutenberg disabled

The new spinner shows up with latest Gutenberg enabled

[github-actions]

Great news! One last step: head over to your WordPress.com diff, D79872-code, and deploy it.
Once you've done so, come back to this PR and add a comment with your changeset ID.

Thank you!

[retrofox]

One last step: head over to your WordPress.com diff, D79872-code, and deploy it.

r244781-wpcom