cfpb-notification: Add color contrast safe colors for links in an error notification

[anselmbradford]

Fixes #1943

The standard link color on a red background in the alert notifications is not accessible.

Changes

• cfpb-notification: Add color contrast safe colors for links in an error notification

Testing

1. PR checks should pass. Visit the alert page in the PR preview and run Google Lighthouse and it should pass the accessibility check with 100%.

[netlify]

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[chosak]

Thank you! For posterity we should note that this PR closes #1943.