Remove sorting by priority before filling.

We can't fill lower-priority zones until the higher-priority ones
have been tesselated, and as the tesselation step always gets pushed
to the back of the queue after the fill finishes having them sorted
by priority accomplishes little.  (We're also going to push all other
layers of the high-priority zone to the back as the first layer will
have the lock, further degrading the usefulness of sorting.)

pcbnew/zone.cpp

@@ -1107,7 +1107,6 @@ bool ZONE::BuildSmoothedPoly( SHAPE_POLY_SET& aSmoothedPoly, PCB_LAYER_ID aLayer
 
     auto smooth = [&]( SHAPE_POLY_SET& aPoly )
                   {
-
                       if( !smooth_requested )
                           return;
 

pcbnew/zone_filler.cpp

@@ -156,14 +156,6 @@ bool ZONE_FILLER::Fill( std::vector<ZONE*>& aZones, bool aCheck, wxWindow* aPare
             static_cast<PCB_VIA*>( track )->ClearZoneConnectionCache();
     }
 
-    // Sort by priority to reduce deferrals waiting on higher priority zones.
-    //
-    std::sort( aZones.begin(), aZones.end(),
-               []( const ZONE* lhs, const ZONE* rhs )
-               {
-                   return lhs->HigherPriority( rhs );
-               } );
-
     for( ZONE* zone : aZones )
     {
         // Rule areas are not filled