Fix Embedded, bump 6.3 Swift toolchain in `test.yml` #2494

Job	Run time
Test BridgeJS against Swift versions (swift:6.2, 602.0.0)	3m 8s
build-examples	8m 44s
Test BridgeJS against Swift versions (swift:6.1.2, 601.0.0)	2m 58s
format	32s
Build and Test (ubuntu-22.04, https://download.swift.org/swift-6.1-release/ubuntu2204/swift-6.1-R...	13m 40s
Build and Test (ubuntu-24.04, https://download.swift.org/swift-6.3-branch/ubuntu2404/swift-6.3-DE...	13m 11s
Build for native target (macos-15, Xcode_16.4)	2m 43s
Build and Test (ubuntu-22.04, https://download.swift.org/development/ubuntu2204/swift-DEVELOPMENT...	17m 44s
Build and Test (ubuntu-24.04, https://download.swift.org/development/ubuntu2404/swift-DEVELOPMENT...	13m 18s
check-bridgejs-generated	2m 34s
prettier	7s
deploy-examples	0s
	1h 18m 39s

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