At #10857 a gitignore codeblock was added. Addition seems correct,
but a pygment formatting was defined as:
.. code-block:: gitignore
No such a pygment exists, and although there is an aditional
package that could parse git-related files, we chose to
not add an extra package dependency for building the docs.
Fallback to unixconfig instead.
Closes#10989
06dbbeb15e