Omit step argument

Following update 614b427 of `Contour_531`.

Inst_eddies/good_contour.f90

@@ -56,7 +56,7 @@ contains
        n_out = 0
     end if
 
-    call find_contours_reg_grid(corner, [1., 1.], z, level, contours, zmax)
+    call find_contours_reg_grid(corner, z, level, contours, zmax)
     n_cont = size(contours)
     found_good_contour = .false.
     i = 1