Upgrade GitHub Actions for Node 24 compatibility #962

Job	Run time
pod-lib-lint (macos-15, GoogleSignIn.podspec, --use-static-frameworks)	14m 50s
spm-build-test (macos-15, iphonesimulator)	2m 42s
pod-lib-lint (macos-15, GoogleSignIn.podspec)	11m 47s
pod-lib-lint (macos-15, GoogleSignInSwiftSupport.podspec)	7m 25s
pod-lib-lint (macos-15, GoogleSignInSwiftSupport.podspec, --use-static-frameworks)	6m 38s
spm-build-test (macos-15, macosx)	2m 29s
	45m 51s

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