Missing a new line after subtitles in ``Paragraph``

[clatapie]

Description of the modifications

Double new lines are not accepted in Paragraph element for rendering purpose.

However, a few titles don't render correctly due to this modification:

**Using PRNLD in a Spectrum or PSD Analysis ( ANTYPE, SPECTR)**
When using :ref:`prnld` in a spectrum analysis (after the combination file has been input through
:ref:`input`,,MCOM and when :ref:`spopt` has not been issued with ``Elcalc`` = YES during the
spectrum analysis), or in a PSD analysis when postprocessing 1-sigma results (loadstep 3, 4, or 5),
the following message will display in the printout header:

Previous example renders as:

Useful links and references

Mentioned in ansys/pymapdl#4003 (comment).