Fix #8744

Marlin/src/gcode/bedlevel/abl/G29.cpp

       abl_grid_points_y = parser.intval('Y', GRID_MAX_POINTS_Y);
       if (parser.seenval('P')) abl_grid_points_x = abl_grid_points_y = parser.value_int();
 
-      if (abl_grid_points_x < 2 || abl_grid_points_y < 2) {
-        SERIAL_PROTOCOLLNPGM("?Number of probe points is implausible (2 minimum).");
+      if (!WITHIN(abl_grid_points_x, 2, GRID_MAX_POINTS_X)) {
+        SERIAL_PROTOCOLLNPGM("?Probe points (X) is implausible (2-" STRINGIFY(GRID_MAX_POINTS_X) ").");
+        return;
+      }
+      if (!WITHIN(abl_grid_points_y, 2, GRID_MAX_POINTS_Y)) {
+        SERIAL_PROTOCOLLNPGM("?Probe points (Y) is implausible (2-" STRINGIFY(GRID_MAX_POINTS_Y) ").");
         return;
       }