fix: point rust-sdks to livekit-ffi/v0.12.56 #49

Job	Run time
Tag release	0s
Build Protocol	0s
Build Protocol docs	0s
Publish livekit-api	0s
Build RTC sdist	0s
Build API	0s
Publish livekit (RTC)	0s
Publish livekit-protocol	0s
Build RTC docs	0s
Build API docs	0s
Detect package	-6s
Create release PR	-8s
Build RTC wheels (${{ matrix.archs }})	-8s
	-22s

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