docs: spurious favicon in template

### Issue type Documentation Bug ### Have you reproduced the bug with TensorFlow Nightly? No ### Source source ### TensorFlow version N/A ### Custom code No ### OS platform and distribution _No response_ ### Mobile device _No response_ ### Python version _No response_ ### Bazel version _No response_ ### GCC/compiler version _No response_ ### CUDA/cuDNN version _No response_ ### GPU model and memory _No response_ ### Current behavior? I can’t work out where the template for this lives, but the Tensorflow docs (at least the homepage and a couple of random pages I spot-checked; some examples include https://www.tensorflow.org/ and https://www.tensorflow.org/js , but I didn’t do an exhaustive search) have a spurious favicon link to an image that doesn’t exist:

<link href="/static/en/site-assets/images/marketing/favicon.png" rel="shortcut icon"/>

This is shadowed by another `` page earlier in the head and so doesn’t seem to be causing any immediate problems, but it still seems like it might be a good idea to clean it up. ### Standalone code to reproduce the issue ```shell curl -s https://www.tensorflow.org | grep 'rel="shortcut icon"' ``` ### Relevant log output ```shell ```