[DFT] add description for assignment operators in table

source/elements/oneMKL/source/domains/dft/descriptor.rst

@@ -123,7 +123,7 @@ The ``descriptor`` class is defined in the ``oneapi::mkl::dft`` namespace.
  :math:`d`-dimensional DFT of user-defined length(s)
  :math:`\lbrace n_1, \ldots, n_d\rbrace`.
  * - :ref:`assignment operators<onemkl_dft_descriptor_assignment_operator>`
- - Self-explanatory.
+ - Performs a deep copy of or moves the argument.
  * - :ref:`onemkl_dft_descriptor_set_value`
  - Sets a configuration value for a specific configuration parameter.
  * - :ref:`onemkl_dft_descriptor_get_value`