Revert of Move gn _run target generation into test().

ui/app_list/BUILD.gn

Index: ui/app_list/BUILD.gn
diff --git a/ui/app_list/BUILD.gn b/ui/app_list/BUILD.gn
index b90ba0e69b933abb9ec5cada8fb81c90caa18c16..e66b9c3db322ff936051bfdd34a1a242c65fc22c 100644
--- a/ui/app_list/BUILD.gn
+++ b/ui/app_list/BUILD.gn
@@ -267,6 +267,15 @@
   }
 }
 
+# TODO(GYP): Delete this after we've converted everything to GN.
+# The _run targets exist only for compatibility w/ GYP.
+group("app_list_unittests_run") {
+  testonly = true
+  deps = [
+    ":app_list_unittests",
+  ]
+}
+
 test("app_list_unittests") {
   sources = [
     "app_list_item_list_unittest.cc",