Cosmetic changes (2) (#20876)

Marlin/Configuration.h

     #define MESH_TEST_LAYER_HEIGHT   0.2  // (mm) Default layer height for the G26 Mesh Validation Tool.
     #define MESH_TEST_HOTEND_TEMP  205    // (°C) Default nozzle temperature for the G26 Mesh Validation Tool.
     #define MESH_TEST_BED_TEMP      60    // (°C) Default bed temperature for the G26 Mesh Validation Tool.
-    #define G26_XY_FEEDRATE        100    // (mm/s) Feedrate for XY Moves for the G26 Mesh Validation Tool.
+    #define G26_XY_FEEDRATE         20    // (mm/s) Feedrate for XY Moves for the G26 Mesh Validation Tool.
     #define G26_RETRACT_MULTIPLIER   1.0  // G26 Q (retraction) used by default between mesh test elements.
   #endif