Forms page updates

[nataliafitzgerald]

I'm in the process of reviewing the forms page for consistency compared with what's built in CF and wth our design intent. This is another batch of updates.

Additions

• Added missing "action" minicon to "Action" notification

Removals

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Changes

• Removed "Error" from text input states. Now appears only in "Notifications" section on the page.
• Moved "Placeholder text" guidance to higher position within the "Helper text" section
• Corrected specs for "Action" notification
• Updated background color for "Disabled" states for radio buttons and checkboxes (standard and large target).

Testing

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Review

• @ielerol

Preview this PR without the whitespace changes

Screenshots

Notes

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Todos

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Checklist

• [ ] Changes are limited to a single goal (no scope creep)
• [ ] Code can be automatically merged (no conflicts)
• [ ] Code follows the standards laid out in the front end playbook
• [ ] Passes all existing automated tests
• [ ] New functions include new tests
• [ ] New functions are documented (with a description, list of inputs, and expected output)
• [ ] Placeholder code is flagged
• [ ] Visually tested in supported browsers and devices
• [ ] Project documentation has been updated (including the "Unreleased" section of the CHANGELOG)