CLN:replace single with double backticks
#36617


    doc/source/development/contributing.rst
    doc/source/development/contributing_docstring.rst
    doc/source/development/extending.rst
    doc/source/ecosystem.rst
    doc/source/getting_started/install.rst
    doc/source/getting_started/comparison/comparison_with_sql.rst
    doc/source/getting_started/intro_tutorials/06_calculate_statistics.rst
    doc/source/getting_started/intro_tutorials/08_combine_dataframes.rst
    doc/source/user_guide/categorical.rst

@satrio-hw The doc build for this seems to be failing, note that cross-referencing syntax like :class:\`Series\` _does_ use single backticks: https://www.sphinx-doc.org/en/master/usage/restructuredtext/roles.html#xref-syntax Thanks @satrio-hw for the PR but the issue is now fixed