fix: point rust-sdks to livekit-ffi/v0.12.56 #1406

Job	Run time
Generating protobuf	25s
Build RTC wheels (x86_64 arm64)	1m 19s
Make RTC sdist	12s
Build RTC wheels (AMD64)	1m 37s
Build RTC wheels (x86_64)	58s
Build RTC wheels (aarch64)	1m 24s
Test (ubuntu-latest, Python 3.12) / Test (ubuntu-latest, Python 3.12)	26s
Test (ubuntu-latest, Python 3.11) / Test (ubuntu-latest, Python 3.11)	33s
Test (ubuntu-latest, Python 3.14) / Test (ubuntu-latest, Python 3.14)	33s
Test (windows-latest, Python 3.9) / Test (windows-latest, Python 3.9)	1m 27s
Test (macos-latest, Python 3.12) / Test (macos-latest, Python 3.12)	53s
Test (windows-latest, Python 3.12) / Test (windows-latest, Python 3.12)	1m 26s
Test (macos-latest, Python 3.9) / Test (macos-latest, Python 3.9)	57s
Test (macos-latest, Python 3.14) / Test (macos-latest, Python 3.14)	42s
Test (windows-latest, Python 3.14) / Test (windows-latest, Python 3.14)	52s
Test (ubuntu-latest, Python 3.9) / Test (ubuntu-latest, Python 3.9)	42s
Test (ubuntu-latest, Python 3.13) / Test (ubuntu-latest, Python 3.13)	31s
Test (ubuntu-latest, Python 3.10) / Test (ubuntu-latest, Python 3.10)	26s
Publish RTC release	0s
docs	-1s
	15m 22s

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