[Infra] Update mlmodeldownloader workflow to use macOS 15 for Xcode 16 #2238

Job	Run time
catalyst	2m 48s
pod-lib-lint (ios, macos-14, Xcode_15.2)	10m 32s
mlmodeldownloader-sample-build-test	9m 8s
pod-lib-lint (ios, macos-15, Xcode_16.1)	6m 23s
spm-package-resolved	1m 12s
pod-lib-lint (tvos, macos-14, Xcode_15.2)	7m 13s
pod-lib-lint (tvos, macos-15, Xcode_16.1)	5m 48s
pod-lib-lint (macos, macos-14, Xcode_15.2)	6m 33s
pod-lib-lint (macos, macos-15, Xcode_16.1)	4m 35s
pod-lib-lint (watchos, macos-14, Xcode_15.2)	4m 1s
pod-lib-lint (watchos, macos-15, Xcode_16.1)	2m 30s
spm (macos-13, Xcode_15.2, iOS)	5m 48s
spm (macos-14, Xcode_15.4, iOS)	7m 18s
spm (macos-15, Xcode_16.1, iOS)	2m 5s
spm (macos-15, Xcode_16.1, tvOS)	2m 27s
spm (macos-15, Xcode_16.1, macOS)	1m 36s
spm (macos-15, Xcode_16.1, watchOS)	2m 12s
spm (macos-15, Xcode_16.1, catalyst)	1m 48s
spm (macos-15, Xcode_16.1, visionOS)	2m 5s
mlmodeldownloader-cron-only	0s
	1h 26m 2s

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