Update README.md with new onyx logo assets (#2183)

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Relates to #

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## Checklist

- [ ] The added / edited code has been documented with
[JSDoc](https://jsdoc.app/about-getting-started)
- [ ] All changes are documented in the documentation app (folder
`apps/docs`)
- [ ] If a new component is added, at least one [Playwright screenshot
test](https://github.com/SchwarzIT/onyx/actions/workflows/playwright-screenshots.yml)
is added
- [ ] A changeset is added with `npx changeset add` if your changes
should be released as npm package (because they affect the library
usage)

README.md

@@ -1,8 +1,8 @@
 <div align="center" style="text-align: center">
   <picture>
-    <source media="(prefers-color-scheme: dark)" type="image/svg+xml" srcset="./.github/onyx-logo-light.svg">
-    <source media="(prefers-color-scheme: light)" type="image/svg+xml" srcset="./.github/onyx-logo-dark.svg">
-    <img alt="onyx logo" src="./.github/onyx-logo-dark.svg" width="160px">
+    <source media="(prefers-color-scheme: dark)" type="image/svg+xml" srcset="./.github/onyx-logo_mint_4c.svg">
+    <source media="(prefers-color-scheme: light)" type="image/svg+xml" srcset="./.github/onyx-logo_white_4c.svg">
+    <img alt="onyx logo" src="./.github/onyx-logo_mint_4c.svg" width="160px">
   </picture>
 </div>