Move experimental (#2680)

Removes the remaining samples in `experimental`. They're now in the
flutter/demos repository.

*List which issues are fixed by this PR. For larger changes, raising an
issue first helps
reduce redundant work.*

#2520 

## 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 have added sample code updates to the [changelog].
- [x] I updated/added relevant documentation (doc comments with `///`).

tool/flutter_ci_script_stable.sh

@@ -29,16 +29,6 @@ declare -ar PROJECT_NAMES=(
     "desktop_photo_search/fluent_ui"
     "desktop_photo_search/material"
     "dynamic_theme"
-    "experimental/federated_plugin/federated_plugin"
-    "experimental/federated_plugin/federated_plugin/example"
-    "experimental/federated_plugin/federated_plugin_macos"
-    "experimental/federated_plugin/federated_plugin_platform_interface"
-    "experimental/federated_plugin/federated_plugin_web"
-    "experimental/federated_plugin/federated_plugin_windows"
-    "pedometer"
-    "pedometer/example"
-    "experimental/varfont_shader_puzzle"
-    "experimental/web_dashboard"
     "flutter_maps_firestore"
     "form_app"
     "game_template"
@@ -46,11 +36,13 @@ declare -ar PROJECT_NAMES=(
     "google_maps"
     "infinite_list"
     "ios_app_clip"
-    "isolate_example"
-    "material_3_demo"
+    # "isolate_example"
+    # "material_3_demo"
     "navigation_and_routing"
+    "pedometer"
+    "pedometer/example"
     "place_tracker"
-    "platform_channels"
+    # "platform_channels"
     "platform_design"
     "platform_view_swift"
     "provider_counter"