[Serve] Reword no Spot Policy in SkyServe #15078

Job	Run time
python-test (3.8, tests/unit_tests)	5m 30s
python-test (3.8, tests/test_api.py)	3m 28s
python-test (3.8, tests/test_cli.py)	3m 36s
python-test (3.8, tests/test_config.py)	3m 18s
python-test (3.8, tests/test_global_user_state.py)	3m 3s
python-test (3.8, tests/test_jobs.py)	3m 53s
python-test (3.8, tests/test_list_accelerators.py)	3m 41s
python-test (3.8, tests/test_optimizer_dryruns.py)	5m 6s
python-test (3.8, tests/test_optimizer_random_dag.py)	3m 54s
python-test (3.8, tests/test_storage.py)	3m 6s
python-test (3.8, tests/test_wheels.py)	3m 22s
python-test (3.8, tests/test_jobs_and_serve.py)	3m 11s
python-test (3.8, tests/test_yaml_parser.py)	3m 11s
	48m 19s

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