Fix Embedded, bump 6.3 Swift toolchain in `test.yml` #2499

Job	Run time
Build and Test (ubuntu-24.04, https://download.swift.org/swift-6.3-branch/ubuntu2404/swift-6.3-DE...	12m 3s
Build and Test (ubuntu-22.04, https://download.swift.org/development/ubuntu2204/swift-DEVELOPMENT...	17m 36s
prettier	9s
Build and Test (ubuntu-22.04, https://download.swift.org/swift-6.1-release/ubuntu2204/swift-6.1-R...	13m 23s
check-bridgejs-generated	2m 41s
Build and Test (ubuntu-24.04, https://download.swift.org/development/ubuntu2404/swift-DEVELOPMENT...	11m 59s
build-examples	21m 17s
format	35s
Build for native target (macos-15, Xcode_16.4)	2m 21s
Test BridgeJS against Swift versions (swift:6.1.2, 601.0.0)	3m 4s
Test BridgeJS against Swift versions (swift:6.2, 602.0.0)	3m 20s
deploy-examples	0s
	1h 28m 28s

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