[Draft] Silence LGTM warnings about unused vars

LGTM only recognizes "_" and "unused" as variable names that are
expected to be unused, so switch to "_".

src/Mod/Draft/draftgeoutils/sort_edges.py

@@ -92,7 +92,7 @@ def sortEdges(edges):
     ret = list()
     # store the hash code of the last edge, to avoid picking the same edge back
     eh = None
-    for i in range(len(nedges)):
+    for _ in range(len(nedges)):
         try:
             eset = sdict[v]
             e = eset.pop()

src/Mod/Draft/draftguitools/gui_trimex.py

@@ -123,7 +123,7 @@ class Trimex(gui_base_original.Modifier):
             self.extrudeMode = True
             self.ghost = [trackers.ghostTracker([self.obj])]
             self.normal = self.obj.Shape.Faces[0].normalAt(0.5, 0.5)
-            self.ghost += [trackers.lineTracker() for _v in self.obj.Shape.Vertexes]
+            self.ghost += [trackers.lineTracker() for _ in self.obj.Shape.Vertexes]
         elif len(self.obj.Shape.Faces) > 1:
             # face extrude mode, a new object is created
             ss = Gui.Selection.getSelectionEx()[0]
@@ -134,7 +134,7 @@ class Trimex(gui_base_original.Modifier):
                     self.extrudeMode = True
                     self.ghost = [trackers.ghostTracker([self.obj])]
                     self.normal = self.obj.Shape.Faces[0].normalAt(0.5, 0.5)
-                    self.ghost += [trackers.lineTracker() for _v in self.obj.Shape.Vertexes]
+                    self.ghost += [trackers.lineTracker() for _ in self.obj.Shape.Vertexes]
         else:
             # normal wire trimex mode
             self.color = self.obj.ViewObject.LineColor