Clean up G26 external references, private vars

Marlin/Marlin_main.cpp

@@ -490,8 +490,6 @@ static uint8_t target_extruder;
   float zprobe_zoffset = Z_PROBE_OFFSET_FROM_EXTRUDER;
 #endif
 
-#define PLANNER_XY_FEEDRATE() (min(planner.max_feedrate_mm_s[X_AXIS], planner.max_feedrate_mm_s[Y_AXIS]))
-
 #if HAS_ABL
   float xy_probe_feedrate_mm_s = MMM_TO_MMS(XY_PROBE_SPEED);
   #define XY_PROBE_FEEDRATE_MM_S xy_probe_feedrate_mm_s