Installing scipy-wheels-nightly using pip shows error

### Describe the bug

When installing torch from https://pypi.anaconda.org/scipy-wheels-nightly/simple the console show a warning.

### Steps/Code to Reproduce

```bash
~: pip install --pre --extra-index https://pypi.anaconda.org/scipy-wheels-nightly/simple scikit-learn
Looking in indexes: https://pypi.org/simple, https://pypi.anaconda.org/scipy-wheels-nightly/simple
warning: missing-index-doctype

× The package index page being used does not have a proper HTML doctype declaration.
╰─> Problematic URL: https://pypi.anaconda.org/scipy-wheels-nightly/simple/scikit-learn/

note: This is an issue with the page at the URL mentioned above.
hint: You might need to reach out to the owner of that package index, to get this fixed. See https://github.com/pypa/pip/issues/10825 for context.
Collecting scikit-learn
  Downloading https://pypi.anaconda.org/scipy-wheels-nightly/simple/scikit-learn/1.1.dev0/scikit_learn-1.1.dev0-cp39-cp39-macosx_12_0_arm64.whl (7.4 MB)
     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 7.4/7.4 MB 2.8 MB/s eta 0:00:00
```

### Expected Results

No warning is shown

### Actual Results

```bash
warning: missing-index-doctype

× The package index page being used does not have a proper HTML doctype declaration.
╰─> Problematic URL: https://pypi.anaconda.org/scipy-wheels-nightly/simple/scikit-learn/

note: This is an issue with the page at the URL mentioned above.
hint: You might need to reach out to the owner of that package index, to get this fixed. See https://github.com/pypa/pip/issues/10825 for context.
```

### Versions

```shell
Python 3.9.10 (main, Jan 15 2022, 11:40:53) 
[Clang 13.0.0 (clang-1300.0.29.3)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import sklearn; sklearn.show_versions()

System:
    python: 3.9.10 (main, Jan 15 2022, 11:40:53)  [Clang 13.0.0 (clang-1300.0.29.3)]
executable: /opt/homebrew/opt/python@3.9/bin/python3.9
   machine: macOS-12.2.1-arm64-arm-64bit

Python dependencies:
      sklearn: 1.1.dev0
          pip: 22.0.3
   setuptools: 60.9.3
        numpy: 1.21.4
        scipy: 1.7.3
       Cython: None
       pandas: 1.4.0
   matplotlib: None
       joblib: 1.1.0
threadpoolctl: 3.0.0

Built with OpenMP: True

threadpoolctl info:
       user_api: openmp
   internal_api: openmp
         prefix: libomp
       filepath: /opt/homebrew/lib/python3.9/site-packages/sklearn/.dylibs/libomp.dylib
        version: None
    num_threads: 8

       user_api: blas
   internal_api: openblas
         prefix: libopenblas
       filepath: /opt/homebrew/lib/python3.9/site-packages/numpy/.dylibs/libopenblas.0.dylib
        version: 0.3.17
threading_layer: pthreads
   architecture: armv8
    num_threads: 8

       user_api: blas
   internal_api: openblas
         prefix: libopenblas
       filepath: /opt/homebrew/lib/python3.9/site-packages/scipy/.dylibs/libopenblas.0.dylib
        version: 0.3.17
threading_layer: pthreads
   architecture: armv8
    num_threads: 8
```

COMMENT:
@ogrisel Do you know who can resolve this issue on https://pypi.anaconda.org/scipy-wheels-nightly/simple ?

Labels: Bug, Packaging