Decrease time step for manufactured solution

Author: cbegeman

polaris/ocean/tasks/manufactured_solution/manufactured_solution.cfg

@@ -25,7 +25,7 @@ n_wavelengths_x = 2
 n_wavelengths_y = 2
 
 # Time step per resolution (s/km), since dt is proportional to resolution
-dt_per_km = 3.0
+dt_per_km = 1.5
 
 # Convergence threshold below which the test fails
 conv_thresh = 1.8