Simplify samples index and remove cookbook recipes (#2102)

Remove the cookbook recipes from the samples index in a step to
eventually remove it as a whole.

The cookbook recipe listings in the index haven't been updated in a long
time, the support for updating them doesn't work, and this isn't
generally how people are finding cookbook recipes.

This has the added benefit of reducing repo size quite a bit due to the
large images.

web/samples_index/lib/src/data.dart

@@ -36,11 +36,10 @@ class Sample {
   /// The author of the sample. Typically "Flutter"
   final String? author;
 
-  /// Screenshots of the sample or cookbook article. At least 1 screenshot is
-  /// required.
+  /// Screenshots of the sample. At least 1 screenshot is required.
   final List<Screenshot> screenshots;
 
-  /// A link to the source code or cookbook article if type is 'cookbook'.
+  /// A link to the source code.
   final String source;
 
   /// A link to this sample running in the browser.
@@ -69,7 +68,7 @@ class Sample {
   final List<String> platforms;
 
   /// The type of the sample. Supported values are either 'sample' or
-  /// 'cookbook'.
+  /// 'demo'.
   final String type;
 
   /// The date this sample was created.

web/samples_index/lib/src/templates.dart

@@ -110,12 +110,6 @@ String _indexBody(List<Sample> samples) => '''
                 <span role="button" tabindex="-1" class="mdc-chip__text">Sample</span>
               </span>
             </div>
-            <div class="mdc-chip" role="row">
-              <div class="mdc-chip__ripple"></div>
-              <span role="gridcell">
-                <span role="button" tabindex="-1" class="mdc-chip__text">Cookbook</span>
-              </span>
-            </div>
             <div class="mdc-chip" role="row">
               <div class="mdc-chip__ripple"></div>
               <span role="gridcell">
@@ -205,11 +199,6 @@ String _descriptionButtons(Sample sample) {
 <span class="mdc-button__label">Source Code</span>
 </button>''');
   }
-
-  if (sample.type == 'cookbook') {
-    buf.write(
-        '''<button class="mdc-button mdc-button--outlined" onclick="window.location.href = '${sample.source}';">  <span class="mdc-button__ripple"></span>View Recipe</button>''');
-  }
   return buf.toString();
 }