fix: pymupdf must be optional because is AGPLv3 licensed (#11896)

docs/examples/agent/openai_retrieval_benchmark.ipynb

docs/examples/finetuning/gradient/gradient_structured.ipynb

docs/examples/finetuning/openai_fine_tuning_functions.ipynb

docs/examples/low_level/evaluation.ipynb

docs/examples/low_level/fusion_retriever.ipynb

docs/examples/low_level/oss_ingestion_retrieval.ipynb

docs/examples/low_level/response_synthesis.ipynb

docs/examples/low_level/retrieval.ipynb

docs/examples/low_level/router.ipynb

docs/examples/low_level/vector_store.ipynb

docs/examples/param_optimizer/param_optimizer.ipynb

docs/examples/prompts/emotion_prompt.ipynb

docs/examples/prompts/prompt_optimization.ipynb

docs/examples/prompts/prompts_rag.ipynb

...xamples/query_engine/pdf_tables/recursive_retriever.ipynb

docs/examples/retrievers/auto_merging_retriever.ipynb

docs/examples/retrievers/composable_retrievers.ipynb

docs/examples/retrievers/ensemble_retrieval.ipynb

...-readers-file/llama_index/readers/file/pymu_pdf/README.md

...egrations/readers/llama-index-readers-file/pyproject.toml