Fix existential-any for Swift6 #332

Job	Run time
swiftpm (iphoneos, arm64)	18s
build (5.10, 15.4, macos-14)	49s
swiftpm (iphonesimulator, x86_64)	18s
cocoapods	50s
build (5.9, 15.2, macos-13)	59s
example (Maps)	1m 11s
swiftpm (iphonesimulator, arm64)	18s
build (5.8, 14.3.1, macos-13)	1m 9s
example (Maps-SwiftUI)	49s
example (Stocks)	49s
swiftpm_old (x86_64-apple-ios16.4-simulator, 14.3.1, macos-13)	41s
example (Samples)	50s
test (17.5, 15.4, iPhone 15 Pro, NO, macos-14)	1m 34s
swiftpm_old (arm64-apple-ios16.4-simulator, 14.3.1, macos-13)	40s
test (16.4, 14.3.1, iPhone 14 Pro, NO, macos-13)	3m 9s
swiftpm_old (x86_64-apple-ios15.7-simulator, 14.1, macos-12)	36s
test (15.5, 13.4.1, iPhone 13 Pro, NO, macos-12)	28s
build (5.7, 14.1, macos-12)	36s
build (5.6, 13.4.1, macos-12)	31s
build (5.5, 13.2.1, macos-12)	1m 28s
swiftpm_old (arm64-apple-ios15.7-simulator, 14.1, macos-12)	36s
	18m 39s

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