rename use_group macro with additional underscore

doc/environments/groupthm/groupthm.dtx

@@ -2007,12 +2007,10 @@
 % \end{macro}
 %
 %
-%
 % As usual, we provide a \texttt{new} and a \texttt{provide} variant wrapped
 % around this that do proper error checking.
 % 
 % 
-%
 % \begin{macro}
 % {
 %   \groupthm_new_grouped_theorem:nnnn,
@@ -2044,12 +2042,10 @@
 %    \end{macrocode}
 % \end{macro}
 % 
-% 
 %
 %   The star variants of these that add the \texttt{unnumbered} group
 %   are straightforward:
 %
-%
 % \begin{macro}{\groupthm_new_grouped_theorem_star:nnnn}
 %		 
 %    \begin{macrocode}
@@ -2061,7 +2057,6 @@
 %    \end{macrocode}
 % \end{macro}
 %
-%
 % 
 % \begin{macro}{\groupthm_provide_grouped_theorem_star:nnnn}
 %    \begin{syntax}