default to legacy LooperMode

Summary:
D73854866 aims to remove this override from the `robolectric4_test` macro so that the default becomes the non-deprecated PAUSED LooperMode across. But this target times out when the default LooperMode is set to PAUSED.

This diff adds the vm_arg to the target so that it won't start timing out once the override is removed.

More context in this post: https://fb.workplace.com/groups/android.testing.fyi/permalink/2448074072235887/

Reviewed By: cpepin

Differential Revision: D74293898

fbshipit-source-id: 55885d347da5cfc2e0caa70ce5727e3aa0d42447

Author: Carlos Gomez

litho-it/src/test/com/facebook/litho/BUCK

@@ -67,6 +67,9 @@ litho_robolectric4_test(
     source = "8",
     target = "8",
     target_sdk_levels = ["33"],
+    vm_args = [
+        "-Drobolectric.looperMode=LEGACY",
+    ],
     deps = [
         LITHO_GUAVA_TARGET,
         LITHO_ANDROIDSUPPORT_RECYCLERVIEW_TARGET,