Remove unused and incorrect "icon" metadata from definitions

The "icon" metadata is not used, and in all cases points to non-existing files anyway.

resources/definitions/3dator.def.json

@@ -7,7 +7,6 @@
         "author": "3Dator GmbH",
         "manufacturer": "3Dator GmbH",
         "file_formats": "text/x-gcode",
-        "icon": "icon_ultimaker2",
         "supports_usb_connection": true,
         "platform": "3dator_platform.stl",
         "machine_extruder_trains":

resources/definitions/anycubic_i3_mega.def.json

@@ -8,7 +8,6 @@
         "author": "TheTobby",
         "manufacturer": "Anycubic",
         "file_formats": "text/x-gcode",
-        "icon": "icon_ultimaker2",
         "platform": "anycubic_i3_mega_platform.stl",
         "has_materials": false,
         "has_machine_quality": true,

resources/definitions/deltacomb.def.json

@@ -8,7 +8,6 @@
         "manufacturer": "Deltacomb 3D",
         "category": "Other",
         "file_formats": "text/x-gcode",
-        "icon": "icon_ultimaker2",
         "platform": "deltacomb.stl",
         "has_machine_quality": true,
         "machine_extruder_trains":

resources/definitions/fabtotum.def.json

@@ -9,7 +9,6 @@
         "category": "Other",
         "file_formats": "text/x-gcode",
         "platform": "fabtotum_platform.stl",
-        "icon": "fabtotum_platform.png",
         "has_machine_quality": true,
         "has_variants": true,
         "variants_name": "Head",

resources/definitions/grr_neo.def.json

@@ -7,7 +7,6 @@
         "author": "Simon Cor",
         "manufacturer": "German RepRap",
         "file_formats": "text/x-gcode",
-        "icon": "icon_ultimaker.png",
         "platform": "grr_neo_platform.stl",
         "machine_extruder_trains":
         {

resources/definitions/kossel_mini.def.json

@@ -7,7 +7,6 @@
         "author": "Claudio Sampaio (Patola)",
         "manufacturer": "Other",
         "file_formats": "text/x-gcode",
-        "icon": "icon_ultimaker2",
         "platform": "kossel_platform.stl",
         "platform_offset": [0, -0.25, 0],
         "machine_extruder_trains":

resources/definitions/kossel_pro.def.json

@@ -7,7 +7,6 @@
         "author": "Chris Petersen",
         "manufacturer": "OpenBeam",
         "file_formats": "text/x-gcode",
-        "icon": "icon_ultimaker2",
         "platform": "kossel_pro_build_platform.stl",
         "platform_offset": [0, -0.25, 0],
         "machine_extruder_trains":

resources/definitions/makeR_pegasus.def.json

@@ -7,7 +7,6 @@
         "author": "makeR",
         "manufacturer": "makeR",
         "file_formats": "text/x-gcode",
-        "icon": "icon_ultimaker2",
         "platform": "makeR_pegasus_platform.stl",
         "platform_offset": [-200, -10, 200],
         "machine_extruder_trains":

resources/definitions/makeR_prusa_tairona_i3.def.json

@@ -7,7 +7,6 @@
         "author": "makeR",
         "manufacturer": "makeR",
         "file_formats": "text/x-gcode",
-        "icon": "icon_ultimaker2",
         "platform": "makeR_prusa_tairona_i3_platform.stl",
         "platform_offset": [-2, 0, 0],
         "machine_extruder_trains":

resources/definitions/maker_starter.def.json

@@ -7,7 +7,6 @@
         "author": "tvlgiao",
         "manufacturer": "3DMaker",
         "file_formats": "text/x-gcode;application/x-stl-ascii;application/x-stl-binary;application/x-wavefront-obj",
-        "icon": "icon_ultimaker2.png",
         "platform": "makerstarter_platform.stl",
         "preferred_quality_type": "draft",
         "machine_extruder_trains":