update adapt_time_step() docstring
update adapt_time_step() docstring

sfepy/sfepy,lokik/sfepy,vlukes/sfepy,rc/sfepy,vlukes/sfepy,lokik/sfepy,sfepy/sfepy,BubuLK/sfepy,vlukes/sfepy,lokik/sfepy,BubuLK/sfepy,lokik/sfepy,rc/sfepy,BubuLK/sfepy,sfepy/sfepy,rc/sfepy