UI inputs: Fix typings

[tkohr]

This PR fixes some typings in the dropdown-multiselect.component and filter-dropdown.component that cause issues when reusing and extending these components in a different project.

Quality Assurance Checklist

• Commit history is devoid of any merge commits and readable to facilitate reviews
• If new logic ⚙️ is introduced: unit tests were added
• If new user stories 🤏 are introduced: E2E tests were added
• If new UI components 🕹️ are introduced: corresponding stories in Storybook were created
• If breaking changes 🪚 are introduced: add the breaking change label
• If bugs 🐞 are fixed: add the backport <release branch> label
• The documentation website 📚 has received the love it deserves

This work is sponsored by MEL.

[tkohr]

I really don't like this but couldn't find a better solution.

[github-actions]

Affected libs: feature-search, feature-router, feature-map, feature-dataviz, feature-record, ui-inputs, feature-editor, ui-elements, feature-catalog, ui-catalog, ui-search,
Affected apps: metadata-editor, datahub, demo, webcomponents, search, map-viewer, metadata-converter, datafeeder,

• 🚀 Build and deploy storybook and demo on GitHub Pages
• 📦 Build and push affected docker images

[coveralls]

coverage: 82.132% (-1.8%) from 83.944%
when pulling 2ecc94d on dropdown-types
into ca02804 on main.

[jahow]

Reworked in pair programming!

[tkohr]

Thanks for the help finding a better solution @jahow !