[fix] Args section is empty in codac_py_XXX_docs headers

[benEnsta]

When doc files are generate, the "Args" section of docstring is empty.

For instance with the generated file "codac_py_Slice_docs.h", I got

// std::ostream& operator<<(std::ostream &str, const Slice &x)
const char* SLICE_OSTREAM_OPERATOR_OSTREAM_SLICE = R"_docs(Displays a synthesis of this slice.

Args:

Returns:
  ostream.
)_docs";

instead of

// std::ostream& operator<<(std::ostream &str, const Slice &x)
const char* SLICE_OSTREAM_OPERATOR_OSTREAM_SLICE = R"_docs(Displays a synthesis of this slice.

Args:
  str (ostream): ostream.
  x (Slice): slice to be displayed.

Returns:
  ostream.
)_docs";