docs/web-ui: drop the redundant Topology tree section

C0NTAINERS already states the flat/alphabetical/no-nesting fact;
the section repeated it with zero new operator info. Fix the two
dangling references (README.md reading-path index, swarm.js
comment) rather than leaving them pointing at a removed heading.

docs/web-ui/README.md

@@ -115,8 +115,7 @@ touching the code rather than using the UI:
   [`shape.md`](shape.md) (SSE multiplexing, Worker-death self-heal,
   atomic repaint).
 - **"What does a container row contain?"** →
-  [`dashboard.md`](dashboard.md) (Container row, Topology tree,
-  Selection bar).
+  [`dashboard.md`](dashboard.md) (Container row, Selection bar).
 - **"What endpoints does the dashboard expose?"** →
   [`dashboard.md`](dashboard.md) (Dashboard endpoints, Dashboard event
   channel).