Cleanup: remove gizmo transform workaround which is no longer needed

Now gizmos forward the original event to transform so assuming an LMB
event is no longer needed.

source/blender/editors/transform/transform.c

@@ -1786,13 +1786,6 @@ bool initTransform(bContext *C, TransInfo *t, wmOperator *op, const wmEvent *eve
   t->launch_event = event ? WM_userdef_event_type_from_keymap_type(event->type) : -1;
   t->is_launch_event_drag = event ? (event->val == KM_CLICK_DRAG) : false;
 
-  /* XXX Remove this when wm_operator_call_internal doesn't use window->eventstate
-   * (which can have type = 0) */
-  /* For gizmo only, so assume LEFTMOUSE. */
-  if (t->launch_event == 0) {
-    t->launch_event = LEFTMOUSE;
-  }
-
   unit_m3(t->spacemtx);
 
   initTransInfo(C, t, op, event);