Address sass deprecation warnings

[jessicamcinchak]

Seems like these are still around even with the recent major version bump of govuk-frontend

Would like to better understand:

• Do we have any redundant/unnecessary style imports? logs have noticable duplicates, not sure what's source code versus us
• Can we get to component-level imports rather than global? eg https://github.com/theopensystemslab/map/blob/main/src/components/postcode-search/styles.scss#L2
• Options for hiding/resolving/clearing these warnings from logs? (adds a lot of noise to pnpm dev, pnpm test, pnpm build etc)