Don't correct bed origin any more

It's not needed with current versions of the Printrbot Simple version of Marlin, or even the version that the printers are shipped with. Thanks to tenten8401 for the debugging.

Fixes #3711.

resources/definitions/printrbot_simple.def.json

@@ -32,7 +32,7 @@
         "machine_gcode_flavor": { "default_value": "RepRap (Marlin/Sprinter)" },
 
         "machine_start_gcode": {
-            "default_value": "G21       ;metric values\nG90       ;absolute positioning\nM82       ;set extruder to absolute mode\nM107      ;start with the fan off\nG28 X0 Y0 ;home X/Y\nG28 Z0    ;home Z\nG92 E0    ;zero the extruded length\nG29       ;initiate auto bed leveling sequence\nG92 X132.4 Y20 ;correct bed origin (G29 changes it)"
+            "default_value": "G21       ;metric values\nG90       ;absolute positioning\nM82       ;set extruder to absolute mode\nM107      ;start with the fan off\nG28 X0 Y0 ;home X/Y\nG28 Z0    ;home Z\nG92 E0    ;zero the extruded length\nG29       ;initiate auto bed leveling sequence"
         },
         "machine_end_gcode": {
             "default_value": "M104 S0     ;extruder heater off\nM140 S0     ;heated bed heater off (if you have it)\nM106 S0     ;fan off\nG91         ;relative positioning\nG1 E-1 F300 ;retract the filament a bit\nG1 Z+1 E-5 F9000 ;move Z up a bit and retract even more\nG28 X0 Y0   ;home X/Y, so the head is out of the way\nM84         ;steppers off\nG90         ;absolute positioning"