Remove incorrect CDECL declaration from SlotNameSorter

src/tracerestrict_gui.cpp

@@ -506,7 +506,7 @@ static DropDownList GetGroupDropDownList(Owner owner, GroupID group_id, int &sel
 }
 
 /** Sort slots by their name */
-static bool CDECL SlotNameSorter(const TraceRestrictSlot * const &a, const TraceRestrictSlot * const &b)
+static bool SlotNameSorter(const TraceRestrictSlot * const &a, const TraceRestrictSlot * const &b)
 {
 	int r = strnatcmp(a->name.c_str(), b->name.c_str()); // Sort by name (natural sorting).
 	if (r == 0) return a->index < b->index;