Move work_serializer_dispatch dependency to rollouts (#36013)

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Closes #36013

COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/36013 from yousukseung:work-serializer 8fdf679309
PiperOrigin-RevId: 610938472

src/core/lib/experiments/experiments.yaml

@@ -282,7 +282,6 @@
   expiry: 2024/03/31
   owner: ysseung@google.com
   test_tags: ["core_end2end_test", "cpp_end2end_test", "xds_end2end_test", "lb_unit_test"]
-  requires: ["event_engine_client"]
 - name: wrr_delegate_to_pick_first
   description:
     Change WRR code to delegate to pick_first as per dualstack

src/core/lib/experiments/rollouts.yaml

@@ -123,6 +123,7 @@
 - name: work_serializer_clears_time_cache
   default: true
 - name: work_serializer_dispatch
+  requires: ["event_engine_client"]
   default:
     # TODO(ysseung): Not fully tested.
     ios: broken