Move gn _run target generation into test().

ui/base/BUILD.gn

Index: ui/base/BUILD.gn
diff --git a/ui/base/BUILD.gn b/ui/base/BUILD.gn
index 799b57c8918656cb5ae2eaf45e603ce3dcf52608..1ec937128b58c2e15dac70d2f887cd8fd940d6ca 100644
--- a/ui/base/BUILD.gn
+++ b/ui/base/BUILD.gn
@@ -661,16 +661,6 @@ if (is_android) {
   }
 }
 
-#
-# TODO(GYP): Delete this after we've converted everything to GN.
-# The _run targets exist only for compatibility w/ GYP.
-group("ui_base_unittests_run") {
-  testonly = true
-  deps = [
-    ":ui_base_unittests",
-  ]
-}
-
 # GYP version: ui/base/ui_base_tests.gyp:ui_base_unittests
 test("ui_base_unittests") {
   sources = [