langchain

cc4f5269 - docs: replace deprecated llama 3 model with sonar in ChatPerplexity example (#31716)

docs: replace deprecated llama 3 model with sonar in ChatPerplexity example (#31716) **Description:** Updates ChatPerplexity documentation to replace deprecated llama 3 model reference with the current sonar model in the API key example code block. **Issue:** N/A (maintenance update for deprecated model) **Dependencies:** No new dependencies required --------- Co-authored-by: Mason Daugherty <github@mdrxy.com>