Fixed a typo in a comment

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%402266

dlib/optimization/optimization_abstract.h

@@ -198,7 +198,7 @@ namespace dlib
             - x.nc() == 1 (i.e. x must be a column vector)
         ensures
             - Performs an unconstrained minimization of the function f() using a 
-              quasi newton method.  The optimization stops when any of the following
+              conjugate gradient method.  The optimization stops when any of the following
               conditions are satisfied: 
                 - the change in f() from one iteration to the next is less than min_delta
                 - f(#x) <= min_f