fix fixed point example

examples/fixed_point/heat_equation.py

@@ -201,7 +201,6 @@ if __name__=='__main__':
     parser.set_defaults(impl='cl', ndim=3, npts=(32,),
                         box_origin=(0.0,), box_length=(1.,),
                         tstart=0.0, tend=np.pi*2,
-                        dt=1e-1,
-                        dump_freq=100, dump_times=())
+                        dt=1e-1, dump_freq=10)
 
     parser.run(compute)