web/samples_index Drop unused links attribute from config (#1828)

I've confirmed that the `links` configuration attribute is indeed
unused: https://flutter.github.io/samples/next_gen_u_i_demo.html

Dropping unused configuration sounds like a good move. We can
re-introduce it if/when we start displaying the content.

## 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.

If you need help, consider asking for advice on the #hackers-devrel
channel on [Discord].

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[Contributors Guide]:
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web/samples_index/lib/src/data.g.dart

@@ -62,13 +62,6 @@ Sample _$SampleFromJson(Map json) => $checkedCreate(
               (v) =>
                   (v as List<dynamic>?)?.map((e) => e as String).toList() ??
                   const []),
-          links: $checkedConvert(
-              'links',
-              (v) =>
-                  (v as List<dynamic>?)
-                      ?.map((e) => Link.fromJson(e as Map))
-                      .toList() ??
-                  const []),
           type: $checkedConvert('type', (v) => v as String),
           date: $checkedConvert(
               'date', (v) => v == null ? null : DateTime.parse(v as String)),
@@ -90,7 +83,6 @@ Map<String, dynamic> _$SampleToJson(Sample instance) => <String, dynamic>{
       'packages': instance.packages,
       'tags': instance.tags,
       'platforms': instance.platforms,
-      'links': instance.links,
       'type': instance.type,
       'date': instance.date?.toIso8601String(),
       'channel': instance.channel,
@@ -113,20 +105,3 @@ Map<String, dynamic> _$ScreenshotToJson(Screenshot instance) =>
       'url': instance.url,
       'alt': instance.alt,
     };
-
-Link _$LinkFromJson(Map json) => $checkedCreate(
-      'Link',
-      json,
-      ($checkedConvert) {
-        final val = Link(
-          $checkedConvert('text', (v) => v as String),
-          $checkedConvert('href', (v) => v as String),
-        );
-        return val;
-      },
-    );
-
-Map<String, dynamic> _$LinkToJson(Link instance) => <String, dynamic>{
-      'text': instance.text,
-      'href': instance.href,
-    };