[python docs] TensorRT tutorial warnings

[aaronmarkham]

Description

Sphinx builds of the Python API docs have the following warning(s):

/work/mxnet/docs/python_docs/python/build/tutorials/performance/backend/tensorrt/tensorrt.ipynb:272: WARNING: File not found: 'tutorials/performance/backend/tensorrt/_static/tutorials/tensorrt/wavenet_unoptimized.png'
/work/mxnet/docs/python_docs/python/build/tutorials/performance/backend/tensorrt/tensorrt.ipynb:272: WARNING: File not found: 'tutorials/performance/backend/tensorrt/_static/tutorials/tensorrt/wavenet_optimized.png'
/work/mxnet/docs/python_docs/python/build/tutorials/performance/backend/tensorrt/tensorrt.ipynb:295: WARNING: image file not readable: tutorials/performance/backend/tensorrt/wavenet_unoptimized.svg
/work/mxnet/docs/python_docs/python/build/tutorials/performance/backend/tensorrt/tensorrt.ipynb:296: WARNING: image file not readable: tutorials/performance/backend/tensorrt/wavenet_optimized.svg

How to reproduce

You can run into the problem following these steps.

1. Run a "lite" binary build.

ci/build.py --docker-registry mxnetci --platform ubuntu_cpu_lite /work/runtime_functions.sh build_ubuntu_cpu_docs

2. Run the Python API docs build:

ci/build.py --docker-registry mxnetci --platform ubuntu_cpu_python /work/runtime_functions.sh build_python_docs

[mxnet-label-bot]

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Here are my recommended label(s): Doc