Migrate external_deps prettytable to pypi prettytable (#18661) #1449

Job	Run time
test-coreml / test-backend-macos (coreml, operators) / macos-job	16m 8s
test-coreml / test-backend-macos (coreml, models) / macos-job	18m 4s
test-coreml / package-golden-artifacts	0s
test-coreml / test-backend-linux	-6s
	34m 6s

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