style(@dpc-sdp/ripple-ui-forms): stop overscrolling on dropdowns

[lambry]

What I did

• Stop over-scrolling on drop-downs so users don't end up inadvertently scrolling down the page.

Checklist

For all PR's

• [ ] I've added relevant changes to the project Readme if needed.
• [ ] I've updated the documentation site as needed.
• [ ] I have added unit tests to cover my changes (if not applicable, please state why in a comment)

For new components only

• [ ] I have added a story covering all variants
• [ ] I have checked a11y tab in storybook passes
• [ ] Any events are emitted on the event bus

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