Rename GenerativeAISample to VertexAISample #4395

Job	Run time
iOS-Device (macos-12)	8m 21s
iOS-Device (macos-13)	6m 14s
platforms (tvOS, macos-12)	6m 20s
platforms (tvOS, macos-13)	9m 2s
swift-build-run (macos-12)	14m 51s
platforms (tvOS, macos-14)	4m 12s
swift-build-run (macos-13)	7m 29s
platforms (macOS, macos-12)	5m 54s
platforms (macOS, macos-13)	6m 38s
swift-build-run (macos-14, Xcode_15.2, spmbuildonly)	4m 25s
platforms (macOS, macos-14)	3m 32s
platforms (catalyst, macos-12)	6m 48s
platforms (catalyst, macos-13)	6m 56s
platforms (catalyst, macos-14)	3m 47s
platforms (macos-14, visionOS, Xcode_15.2)	5m 51s
	1h 40m 20s

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