BridgeJS: Add missing `function` keyword for namespace function decla… #2170

Job	Run time
check-bridgejs-generated	2m 55s
Test BridgeJS against Swift versions (swift:6.1.2, 601.0.0)	2m 53s
Test BridgeJS against Swift versions (swift:6.2, 602.0.0)	3m 0s
Build for native target (macos-15, Xcode_16.4)	3m 21s
Build and Test (ubuntu-22.04, https://download.swift.org/swift-6.1-release/ubuntu2204/swift-6.1-R...	14m 0s
Build and Test (ubuntu-24.04, https://download.swift.org/swift-6.3-branch/ubuntu2404/swift-6.3-DE...	13m 3s
Build and Test (ubuntu-22.04, https://download.swift.org/development/ubuntu2204/swift-DEVELOPMENT...	16m 57s
format	33s
build-examples	25m 28s
Build and Test (ubuntu-24.04, https://download.swift.org/development/ubuntu2404/swift-DEVELOPMENT...	13m 25s
deploy-examples	9s
	1h 35m 44s

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