Add color declaration for Dialog title

[langermank]

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What are you trying to accomplish?

Addresses part of this bug: https://github.com/github/primer/issues/2473

The title is getting its color from initial which doesn't pull from body in Safari. Might as well just give it a default color.

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• Low risk the change is small, highly observable, and easily rolled back.
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• Fixes axe scan violation - This change fixes an existing axe scan violation.
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Merge checklist

• Added/updated tests
• Added/updated documentation
• Added/updated previews (Lookbook)
• Tested in Chrome
• Tested in Firefox
• Tested in Safari
• Tested in Edge

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🦋 Changeset detected

Latest commit: 7b22e50

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@primer/view-components	Patch

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