update protocol for TimedString #23

Job	Run time
Create release PR	-1s
Build API	-1s
Detect package	-1s
Build RTC wheels (${{ matrix.archs }})	-1s
Build RTC sdist	-1s
Publish livekit-api	0s
Build RTC docs	0s
Tag release	-1s
Publish livekit-protocol	0s
Publish livekit (RTC)	0s
Build Protocol docs	0s
Build API docs	0s
Build Protocol	-8s
	-14s

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