Bump jupyter-sphinx from 0.3.2 to 0.4.0

Bumps jupyter-sphinx from 0.3.2 to 0.4.0.

Commits

• 1bb7d91 release v0.4.0
• 23322c7 Merge pull request #204 from basnijholt/do-not-double-copy
• d40b2ad add paragraph to styling section
• d6ad4d3 add changelog entry
• a0dcbd7 Do not overwrite files in _static if user already has custom versions of thos...
• a74b13e Merge pull request #207 from basnijholt/fix-182
• cfa0879 add deprecation warning
• 75b003f add changelog entry
• 4129ebe rename directives jupyter-download:script -> jupyter-download-script, similar...
• d427c79 Merge pull request #206 from basnijholt/pre-commit
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