Fix Embedded, bump 6.3 Swift toolchain in `test.yml` #2496

Job	Run time
Build for native target (macos-15, Xcode_16.4)	2m 30s
build-examples	21m 13s
Test BridgeJS against Swift versions (swift:6.1.2, 601.0.0)	3m 3s
Build and Test (ubuntu-24.04, https://download.swift.org/swift-6.3-branch/ubuntu2404/swift-6.3-DE...	13m 19s
prettier	12s
Test BridgeJS against Swift versions (swift:6.2, 602.0.0)	3m 5s
format	41s
check-bridgejs-generated	2m 37s
Build and Test (ubuntu-24.04, https://download.swift.org/development/ubuntu2404/swift-DEVELOPMENT...	13m 27s
Build and Test (ubuntu-22.04, https://download.swift.org/development/ubuntu2204/swift-DEVELOPMENT...	16m 16s
Build and Test (ubuntu-22.04, https://download.swift.org/swift-6.1-release/ubuntu2204/swift-6.1-R...	13m 24s
deploy-examples	0s
	1h 29m 47s

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