fix pylint warning '(pointless-string-statement) String statement has no effect'

Python doesn't support docstring for variables directly. Where
appropriate Sphinx style for docstrings for variables is used
'#: some-docstring'

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.. Beremiz documentation master file

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Beremiz's documentation

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=======================

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Contents:

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.. toctree::

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   :maxdepth: 2

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   overview

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   manual/index

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   standards

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