[T/CT] Remove previously unused fixed time output.

Now this feature is used for the given time stepping
algorithm, the sequence of the output files has changed.

Keeping original references.

Tests/Data/Parabolic/ComponentTransport/MassConservation/mass_conservation.prj

@@ -124,7 +124,6 @@
                     <each_steps>300</each_steps>
                 </pair>
             </timesteps>
-            <fixed_output_times> 434629.8 866629.8 1298629.8 1730629.8 2162629.8 2594629.8 </fixed_output_times>
             <output_iteration_results>false</output_iteration_results>
             <variables>
                 <variable>concentration</variable>