deps: bump libserum to 03ef7b5eeb4c2327b5a772f06634e487eb8ed0fc #280

Job	Run time
Detect version	5s
Build libdmdutil-win-x64	3m 4s
Build libdmdutil-win-x86	3m 7s
Build libdmdutil-macos-arm64	50s
Build libdmdutil-macos-x64	1m 24s
Build libdmdutil-linux-x64	1m 7s
Build libdmdutil-linux-aarch64	8m 53s
Build libdmdutil-android-arm64-v8a	33s
Build libdmdutil-ios-arm64	32s
Build libdmdutil-ios-simulator-arm64	30s
Build libdmdutil-tvos-arm64	30s
Build libdmdutil-macos	10s
	20m 45s

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