Move the docs downloading screenshots to LFS

[DragaDoncila]

Description

@jni this PR adds the three recently committed pngs to LFS. It doesn't rewrite history (obviously), but it at least changes them to pointers from now on.

I think I did it right? I just added them to git lfs and then made sure they were listed in git lfs ls-files 🤷‍♀️

Type of change

• Bug-fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

References

How has this been tested?

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• example: all tests pass with my change
• example: I check if my changes works with both PySide and PyQt backends
  as there are small differences between the two Qt bindings.

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• My PR is the minimum possible work for the desired functionality
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• If I included new strings, I have used trans. to make them localizable.
  For more information see our translations guide.

[jni]

Hmmm something seems to be wrong — it should also say "LFS file not shown" in the diff. But I would not be shocked at all to find that GH doesn't render a normal->LFS move correctly. Will check this out locally later today to make sure it works properly for me.

[Carreau]

That seem correct to me:

$ cat <(find . -name '*.png'|sed 's/\.\///g') | grep -v -f <(git lfs ls-files -n | grep '.png'|sort )
napari/resources/logo.png

[jni]

Yup, checked this out and it works...

Why is the CI broken though?

[jni]

Ok, the failing docs issue is caused by #4995, so I'm going to merge. I guess the rest aren't running because no non-docs files are touched. Neat!