Fix high-shields not intercepting indirect fire shells

#2869 adjusted the collision check
used by shields to normalize away the 3D component of positions by default, which in turn
caused high-shields to no longer intercept indirect fire shells. Switch these to use spherical
collision checking to bring back the old behavior.

Source/CombatExtended/CombatExtended/Projectiles/ProjectileCE.cs

@@ -650,7 +650,17 @@ protected bool CheckIntercept(Thing interceptorThing, CompProjectileInterceptor
             {
                 return false;
             }
-            if (CE_Utility.IntersectionPoint(LastPos, newExactPos, shieldPosition, radius, out Vector3[] sect))
+            if (CE_Utility.IntersectionPoint(
+                    LastPos,
+                    newExactPos,
+                    shieldPosition,
+                    radius,
+                    out Vector3[] sect,
+                    // Don't normalize away the 3D component of the projectile position when checking for collisions
+                    // between indirect fire projectiles and shields that protect against them
+                    // (e.g. mortar shells targeting a high-shield).
+                    spherical: interceptorComp.Props.interceptAirProjectiles && def.projectile.flyOverhead
+            ))
             {
                 ExactPosition = newExactPos = sect.OrderBy(x => (OriginIV3.ToVector3() - x).sqrMagnitude).First();
                 landed = true;