✏️ Remove extra G29 line

Followup to 85a62bbf

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

 
       bool zig = PR_OUTER_SIZE & 1;  // Always end at RIGHT and BACK_PROBE_BED_POSITION
 
-      abl.measured_z = 0;
-
       // Outer loop is X with PROBE_Y_FIRST enabled
       // Outer loop is Y with PROBE_Y_FIRST disabled
       for (PR_OUTER_VAR = 0; PR_OUTER_VAR < PR_OUTER_SIZE && !isnan(abl.measured_z); PR_OUTER_VAR++) {