Fix up `web/samples_index` configuration for `next_gen_ui_demo` (#1826)

This PR is required to land for I/O Connect Miami next week.

Context:
https://github.com/flutter/samples/pull/1824#discussion_r1198062978

## Pre-launch Checklist

- [x] I read the [Flutter Style Guide] _recently_, and have followed its
advice.
- [x] I signed the [CLA].
- [x] I read the [Contributors Guide].
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] All existing and new tests are passing.

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channel on [Discord].

<!-- Links -->
[Flutter Style Guide]:
https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo
[CLA]: https://cla.developers.google.com/
[Discord]: https://github.com/flutter/flutter/wiki/Chat
[Contributors Guide]:
https://github.com/flutter/samples/blob/main/CONTRIBUTING.md

---------

Co-authored-by: Parker Lougheed <parlough@gmail.com>

web/samples_index/lib/src/samples.yaml

@@ -666,6 +666,7 @@ samples:
     platforms:
       - Windows, macOS, Linux, web, Android, iOS
     links:
-      - https://codelabs.developers.google.com/codelabs/flutter-next-gen-uis
+      - href: https://codelabs.developers.google.com/codelabs/flutter-next-gen-uis
+        text: Codelab
     type: sample
     web: web/next_gen_ui_demo