fix: correct height that FAWE ends up using for schematics

- this did not end up having an impact on P2 code as it always used getMinBuildHeight when PASTE_ON_TOP was false anyway
 - there should not be any side effects to this as any uses this specific SCHEM_Y value are effectively normalised against it

Core/src/main/java/com/plotsquared/core/generator/HybridPlotWorld.java

@@ -274,7 +274,7 @@ public class HybridPlotWorld extends ClassicPlotWorld {
                 SCHEM_Y = getMinGenHeight();
                 plotY = 0;
             } else if (!Settings.Schematics.PASTE_ON_TOP) {
-                SCHEM_Y = getMinGenHeight();
+                SCHEM_Y = getMinBuildHeight();
                 plotY = 0;
             }
         }