[GCP] Update tpu runtime version for doc (#2602) #4

Job	Run time
python-test (3.8, tests/unit_tests)	2m 49s
python-test (3.8, tests/test_cli.py)	2m 48s
python-test (3.8, tests/test_config.py)	2m 44s
python-test (3.8, tests/test_global_user_state.py)	3m 45s
python-test (3.8, tests/test_jobs.py)	4m 10s
python-test (3.8, tests/test_list_accelerators.py)	2m 55s
python-test (3.8, tests/test_optimizer_dryruns.py)	5m 12s
python-test (3.8, tests/test_optimizer_random_dag.py)	4m 10s
python-test (3.8, tests/test_storage.py)	2m 38s
python-test (3.8, tests/test_wheels.py)	2m 46s
python-test (3.8, tests/test_spot.py)	2m 48s
python-test (3.8, tests/test_yaml_parser.py)	2m 42s
	39m 27s

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