Tweak <Icon /> component

[jessepinho]

The lg size was incorrect, per the Figma designs

[changeset-bot]

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Latest commit: 6dc860f

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[github-actions]

Visit the preview URL for this PR (updated for commit 6dc860f):

https://penumbra-ui-preview--pr1525-jessepinho-icon-j11hnnr6.web.app

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