Move gn _run target generation into test().

ui/touch_selection/BUILD.gn

Index: ui/touch_selection/BUILD.gn
diff --git a/ui/touch_selection/BUILD.gn b/ui/touch_selection/BUILD.gn
index 4d69e18922898d57ae6ca75d44d22c71a105d020..cc273875a4355af15dc33e49f0d1b8ab2f7e1920 100644
--- a/ui/touch_selection/BUILD.gn
+++ b/ui/touch_selection/BUILD.gn
@@ -68,15 +68,6 @@ static_library("test_support") {
   ]
 }
 
-# TODO(GYP): Delete this after we've converted everything to GN.
-# The _run targets exist only for compatibility w/ GYP.
-group("ui_touch_selection_unittests_run") {
-  testonly = true
-  deps = [
-    ":ui_touch_selection_unittests",
-  ]
-}
-
 test("ui_touch_selection_unittests") {
   sources = [
     "longpress_drag_selector_unittest.cc",