Add coordinator for search widget in showcase.

ios/showcase/BUILD.gn

Index: ios/showcase/BUILD.gn
diff --git a/ios/showcase/BUILD.gn b/ios/showcase/BUILD.gn
index f361a1e2e7e1f772449a3eca776bb1d48683b7eb..031b4c473b23e85c03480daf9c8ca2a6d36b0cff 100644
--- a/ios/showcase/BUILD.gn
+++ b/ios/showcase/BUILD.gn
@@ -25,7 +25,6 @@ ios_app_bundle("showcase") {
 
 group("features") {
   deps = [
-    "//ios/chrome/search_widget_extension:search_widget",
     "//ios/clean/chrome/browser/ui/tools:tools_ui",
     "//ios/showcase/content_suggestions",
     "//ios/showcase/ntp",
@@ -36,6 +35,7 @@ group("features") {
     "//ios/showcase/tab_grid",
     "//ios/showcase/toolbar",
     "//ios/showcase/uikit_table_view_cell",
+    "//ios/showcase/widget",
   ]
 }