Triangulate operator: Free memleak

The leak was introduced in the recent changes to
support multiple-object editing.

source/blender/editors/mesh/editmesh_tools.c

@@ -4206,6 +4206,8 @@ static int edbm_quads_convert_to_tris_exec(bContext *C, wmOperator *op)
 		EDBM_update_generic(em, true, true);
 	}
 
+	MEM_freeN(objects);
+
 	return OPERATOR_FINISHED;
 }