Extend SERIAL_CHAR to take multiple arguments

Marlin/src/feature/bedlevel/bedlevel.cpp

@@ -207,8 +207,7 @@ void reset_bed_level() {
         #endif
       }
       #ifdef SCAD_MESH_OUTPUT
-        SERIAL_CHAR(' ');
-        SERIAL_CHAR(']');                     // close sub-array
+        SERIAL_CHAR(' ', ']');                    // close sub-array
         if (y < sy - 1) SERIAL_CHAR(',');
       #endif
       SERIAL_EOL();