BridgeJS: Remove unnecessary helper enums for struct bridging #1987

Job	Run time
check-bridgejs-generated	2m 49s
build-examples	42m 21s
format	31s
Build for native target (macos-15, Xcode_16.4)	2m 46s
Build and Test (ubuntu-22.04, https://download.swift.org/swift-6.1-release/ubuntu2204/swift-6.1-R...	13m 45s
Build and Test (ubuntu-22.04, https://download.swift.org/development/ubuntu2204/swift-DEVELOPMENT...	16m 15s
Build and Test (ubuntu-24.04, https://download.swift.org/swift-6.3-branch/ubuntu2404/swift-6.3-DE...	11m 45s
Build and Test (ubuntu-24.04, https://download.swift.org/development/ubuntu2404/swift-DEVELOPMENT...	13m 18s
deploy-examples	0s
	1h 43m 30s

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