Restore correct G26 values for gMax 1.5+ printer

Marlin/src/config/examples/gCreate/gMax1.5+/Configuration.h

   /**
    * Enable the G26 Mesh Validation Pattern tool.
    */
-  //#define G26_MESH_VALIDATION
+  #define G26_MESH_VALIDATION
   #if ENABLED(G26_MESH_VALIDATION)
-    #define MESH_TEST_NOZZLE_SIZE    0.4  // (mm) Diameter of primary nozzle.
-    #define MESH_TEST_LAYER_HEIGHT   0.2  // (mm) Default layer height for the G26 Mesh Validation Tool.
+    #define MESH_TEST_NOZZLE_SIZE    0.5  // (mm) Diameter of primary nozzle.
+    #define MESH_TEST_LAYER_HEIGHT   0.3  // (mm) Default layer height for the G26 Mesh Validation Tool.
     #define MESH_TEST_HOTEND_TEMP  205.0  // (°C) Default nozzle temperature for the G26 Mesh Validation Tool.
     #define MESH_TEST_BED_TEMP      60.0  // (°C) Default bed temperature for the G26 Mesh Validation Tool.
   #endif