Add non-empty label to avoid over-sized loops (#381)

Work-around to improve the #286 use case.
- https://github.com/wireviz/WireViz/issues/286#issuecomment-2094309143
- https://stackoverflow.com/questions/70996779/graphviz-edges-between-cells-in-the-same-html-table-are-too-long

src/wireviz/Harness.py

@@ -284,6 +284,7 @@ class Harness:
                     dot.edge(
                         f"{connector.name}:p{loop[0]}{loop_side}:{loop_dir}",
                         f"{connector.name}:p{loop[1]}{loop_side}:{loop_dir}",
+                        label=" ",  # Work-around to avoid over-sized loops.
                     )
 
         # determine if there are double- or triple-colored wires in the harness;