Update _html.py

[Lix1993]

Remote duplicated docs

Code PR

• I have read through the contributing notes and understand the structure of the package. In particular, if my PR modifies code of plotly.graph_objects, my modifications concern the codegen files and not generated files.
• I have added tests (if submitting a new feature or correcting a bug) or
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• For a new feature or a change in behaviour, I have updated the relevant docstrings in the code to describe the feature or behaviour (please see the doc checklist as well).

[Lix1993]

fix duplicate doc for write_html, like this:
https://plotly.com/python/interactive-html-export/

[nicolaskruchten]

Thanks!