let's avoid the extra nesting where reasonable

Doc/api/concrete.tex

@@ -192,7 +192,7 @@ There is no \cfunction{PyNone_Check()} function for the same reason.
   header files).
 \end{cfuncdesc}
 
-\subsubsection{Boolean Objects \label{boolObjects}}
+\subsection{Boolean Objects \label{boolObjects}}
 
 Booleans in Python are implemented as a subclass of integers.  There
 are only two booleans, \constant{Py_False} and \constant{Py_True}.  As