Clean up use of extra_xyjerk

Marlin/src/module/planner.cpp

     #endif
     {
       const float jerk = ABS(current_speed[i]),   // cs : Starting from zero, change in speed for this axis
-                  maxj = (max_jerk[i]             // mj : The max jerk setting for this axis
-                    #ifdef TRAVEL_EXTRA_XYJERK
-                      + (i == X_AXIS || i == Y_AXIS ? extra_xyjerk : 0)
-                    #endif
-                  );
-
+                  maxj = (max_jerk[i] + (i == X_AXIS || i == Y_AXIS ? extra_xyjerk : 0.0f)); // mj : The max jerk setting for this axis
       if (jerk > maxj) {                          // cs > mj : New current speed too fast?
         if (limited) {                            // limited already?
           const float mjerk = nominal_speed * maxj; // ns*mj
             : // v_exit <= v_entry                coasting             axis reversal
               ( (v_entry < 0 || v_exit > 0) ? (v_entry - v_exit) : _MAX(-v_exit, v_entry) );
 
-        const float maxj = (max_jerk[axis]
-          #ifdef TRAVEL_EXTRA_XYJERK
-            + (axis == X_AXIS || axis == Y_AXIS ? extra_xyjerk : 0)
-          #endif
-        );
+        const float maxj = (max_jerk[axis] + (axis == X_AXIS || axis == Y_AXIS ? extra_xyjerk : 0.0f));
 
         if (jerk > maxj) {
           v_factor *= maxj / jerk;