Bug fix: remove use of `write_overlap`

The procedure does not exist any longer.

Overlap/overlap.f90

@@ -23,7 +23,6 @@ contains
     use spher_polyline_area_m, only: spher_polyline_area
     use unit_edge_m, only: unit_edge
     use weight_m, only: weight
-    use write_overlap_m, only: write_overlap
 
     type(snapshot), intent(inout):: flow(:) ! (max_delta + 1)
     integer, intent(in):: nlon, nlat