remove wrong examples for MultimodalAgent and VoicePipelineAgent

[yepher]

VPA and MMA are still referenced in README files

grep -ri MultimodalAgent *   
README.md:- **AI voice agents**: `VoicePipelineAgent` and `MultimodalAgent` help orchestrate the conversation flow using LLMs and other AI models.
README.md:We've partnered with OpenAI on a new `MultimodalAgent` API in the Agents framework. This class completely wraps OpenAI’s Realtime API, abstracts away the raw wire protocol, and provide an ultra-low latency WebRTC transport between GPT-4o and your users’ devices. This same stack powers Advanced Voice in the ChatGPT app.
livekit-plugins/livekit-plugins-google/README.md:Gemini Multimodal Live can be used with the `MultimodalAgent` class. See examples/multimodal_agent/gemini_agent.py for an example.
livekit-plugins/livekit-plugins-google/README.md:You can push video frames to your Gemini Multimodal Live session alongside the audio automatically handled by the `MultimodalAgent`.  The basic approach is to subscribe to the video track, create a video stream, sample frames at a suitable frame rate, and push them into the RealtimeSession:
livekit-plugins/livekit-plugins-google/README.md:# Create your MultimodalAgent as usual
livekit-plugins/livekit-plugins-google/README.md:agent = MultimodalAgent(

grep -ri VoicePipelineAgent *
README.md:- **AI voice agents**: `VoicePipelineAgent` and `MultimodalAgent` help orchestrate the conversation flow using LLMs and other AI models.
livekit-plugins/livekit-plugins-turn-detector/README.md:This plugin is designed to be used with the `VoicePipelineAgent`:
livekit-plugins/livekit-plugins-turn-detector/README.md:agent = VoicePipelineAgent(
livekit-plugins/livekit-plugins-llama-index/README.md:    assistant = VoicePipelineAgent(
livekit-plugins/livekit-plugins-speechmatics/README.md:agent = VoicePipelineAgent(

[changeset-bot]

🦋 Changeset detected

Latest commit: c10fa72

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 14 packages

Name	Type
livekit-plugins-elevenlabs	Minor
livekit-plugins-deepgram	Minor
livekit-plugins-cartesia	Patch
livekit-plugins-google	Minor
livekit-plugins-openai	Minor
livekit-plugins-playai	Patch
livekit-plugins-rime	Patch
livekit-plugins-aws	Minor
livekit-agents	Patch
livekit-plugins-groq	Patch
livekit-plugins-azure	Patch
livekit-plugins-turn-detector	Patch
livekit-plugins-neuphonic	Patch
livekit-plugins-anthropic	Patch

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