Remove unused code

The IDs, group, and xlink and such are not used at all.

Contributes to issue CURA-4557.

plugins/ModelChecker/model_checker.svg

@@ -1,10 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<svg width="30px" height="30px" viewBox="0 0 30 30" version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
-    <title>ModelChecker</title>
-    <g id="ModelChecker" stroke="none" fill="none">
-        <polygon fill="#000000" points="19 11 30 8 30 24 19 27"></polygon>
-        <path d="M10,19 C5.581722,19 2,15.418278 2,11 C2,6.581722 5.581722,3 10,3 C14.418278,3 18,6.581722 18,11 C18,15.418278 14.418278,19 10,19 Z M10,17 C13.3137085,17 16,14.3137085 16,11 C16,7.6862915 13.3137085,5 10,5 C6.6862915,5 4,7.6862915 4,11 C4,14.3137085 6.6862915,17 10,17 Z" id="Combined-Shape" fill="#000000"></path>
-        <polygon fill="#000000" points="4.2 15 6 16.8 1.8 21 0 19.2"></polygon>
-        <path d="M18.7333454,8.81666365 C18.2107269,6.71940704 16.9524304,4.91317986 15.248379,3.68790525 L18,3 L30,6 L18.7333454,8.81666365 Z M17,16.6573343 L17,27 L6,24 L6,19.0644804 C7.20495897,19.6632939 8.56315852,20 10,20 C12.8272661,20 15.3500445,18.6963331 17,16.6573343 Z" id="Combined-Shape" fill="#000000"></path>
-    </g>
+<svg width="30px" height="30px" viewBox="0 0 30 30" version="1.1" xmlns="http://www.w3.org/2000/svg">
+    <polygon fill="#000000" points="19 11 30 8 30 24 19 27" />
+    <path d="M10,19 C5.581722,19 2,15.418278 2,11 C2,6.581722 5.581722,3 10,3 C14.418278,3 18,6.581722 18,11 C18,15.418278 14.418278,19 10,19 Z M10,17 C13.3137085,17 16,14.3137085 16,11 C16,7.6862915 13.3137085,5 10,5 C6.6862915,5 4,7.6862915 4,11 C4,14.3137085 6.6862915,17 10,17 Z" fill="#000000" />
+    <polygon fill="#000000" points="4.2 15 6 16.8 1.8 21 0 19.2" />
+    <path d="M18.7333454,8.81666365 C18.2107269,6.71940704 16.9524304,4.91317986 15.248379,3.68790525 L18,3 L30,6 L18.7333454,8.81666365 Z M17,16.6573343 L17,27 L6,24 L6,19.0644804 C7.20495897,19.6632939 8.56315852,20 10,20 C12.8272661,20 15.3500445,18.6963331 17,16.6573343 Z" fill="#000000" />
 </svg>