Remove specialised start g-code from Creality CR-10

By request from Michael.
This makes it the same as the start g-code for the Custom FDM Printer, which apparently works better.

resources/definitions/creality_cr10.def.json

@@ -59,9 +59,6 @@
         "skirt_gap": {
             "default_value": 5
         },
-        "machine_start_gcode": {
-            "default_value": "G21 ;metric values\nG90 ;absolute Positioning\nG28 ; home all axes\nG1 Z5 F3000 ; lift\nG1 X20 Y2 F1500 ; avoid binder clips\nG1 Z0.2 F3000 ; get ready to prime\nG92 E0 ; reset extrusion distance\nG1 X120 E10 F600 ; prime nozzle\nG1 X150 F5000 ; quick wipe"
-        },
         "machine_end_gcode": {
             "default_value": "G91\nG1 F1800 E-3\nG1 F3000 Z10\nG90\nG28 X0 Y0 ; home x and y axis\nM106 S0 ; turn off cooling fan\nM104 S0 ; turn off extruder\nM140 S0 ; turn off bed\nM84 ; disable motors"
         },