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

Co-authored-by: kvid <kvid@users.noreply.github.com>

src/wireviz/wv_harness.py

@@ -323,7 +323,8 @@ class Harness:
                 dot.attr("edge", color="#000000")
                 loops = gv_connector_loops(connector)
                 for head, tail in loops:
-                    dot.edge(head, tail)
+                    dot.edge(head, tail, label=" ")
+                    #                    ^ workaround to avoid oversized loops
 
         # determine if there are double- or triple-colored wires in the harness;
         # if so, pad single-color wires to make all wires of equal thickness