docs: update docstrings in terms_hyperelastic_ul.py for sphinx
docs: update docstrings in terms_hyperelastic_ul.py for sphinx

olivierverdier/sfepy,sfepy/sfepy,lokik/sfepy,rc/sfepy,sfepy/sfepy,RexFuzzle/sfepy,lokik/sfepy,lokik/sfepy,olivierverdier/sfepy,RexFuzzle/sfepy,olivierverdier/sfepy,rc/sfepy,vlukes/sfepy,RexFuzzle/sfepy,BubuLK/sfepy,BubuLK/sfepy,vlukes/sfepy,rc/sfepy,sfepy/sfepy,BubuLK/sfepy,lokik/sfepy,RexFuzzle/sfepy,vlukes/sfepy