Fixed a typo in csg module

modules/csg/csg.cpp

@@ -408,7 +408,7 @@ void CSGBrushOperation::merge_brushes(Operation p_operation, const CSGBrush &p_b
 
 		} break;
 
-		case OPERATION_SUBSTRACTION: {
+		case OPERATION_SUBTRACTION: {
 			int face_count = 0;
 
 			for (int i = 0; i < mesh_merge.faces.size(); i++) {

modules/csg/csg.h

@@ -68,7 +68,7 @@ struct CSGBrushOperation {
 	enum Operation {
 		OPERATION_UNION,
 		OPERATION_INTERSECTION,
-		OPERATION_SUBSTRACTION,
+		OPERATION_SUBTRACTION,
 	};
 
 	void merge_brushes(Operation p_operation, const CSGBrush &p_brush_a, const CSGBrush &p_brush_b, CSGBrush &r_merged_brush, float p_vertex_snap);

modules/csg/csg_shape.cpp

@@ -185,7 +185,7 @@ CSGBrush *CSGShape::_get_brush() {
 						bop.merge_brushes(CSGBrushOperation::OPERATION_INTERSECTION, *n, *nn2, *nn, snap);
 						break;
 					case CSGShape::OPERATION_SUBTRACTION:
-						bop.merge_brushes(CSGBrushOperation::OPERATION_SUBSTRACTION, *n, *nn2, *nn, snap);
+						bop.merge_brushes(CSGBrushOperation::OPERATION_SUBTRACTION, *n, *nn2, *nn, snap);
 						break;
 				}
 				memdelete(n);