Keep only the resulting-duals figure at n=21

Remove the witness-ELG figure (former Fig. 5); keep the six resulting duals
with their introduced green bridge edges. Fix the dangling cross-reference
in the caption.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

papers/even_level_graph_generators/paper.tex

@@ -426,29 +426,16 @@ witnesses are step-verified.}
 \label{tab:n21}
 \end{table}
 
-\begin{figure}[ht]
-\centering
-\includegraphics[width=\textwidth]{figures/n21_elgs.png}
-\caption{The witness Even Level Graph for each of the six Holton--McKay
-duals, drawn as a crossing-free planar graph and coloured by parity (blue
-even, orange odd, with respect to the fixed level-parity labelling). The
-dashed red edges are the same-parity edges that the bridge switches flip;
-flipping them yields the corresponding dual in
-Figure~\ref{fig:n21-duals}. Duals $1$ and $2$ are Even Level Graphs
-outright, so no edge is flipped.}
-\label{fig:n21-elgs}
-\end{figure}
-
 \begin{figure}[ht]
 \centering
 \includegraphics[width=\textwidth]{figures/n21_duals.png}
 \caption{The six Holton--McKay duals, drawn as crossing-free planar graphs
-with the same parity colouring. The solid green edges are the bridge edges
-introduced by the switches from the Even Level Graphs of
-Figure~\ref{fig:n21-elgs}. Each green edge is a bridge of its parity
-subgraph, so no new cycle -- and in particular no odd cycle -- is created;
-duals $1$ and $2$ coincide with their Even Level Graphs and have no added
-edge.}
+and coloured by parity (blue even, orange odd, with respect to the fixed
+level-parity labelling). The solid green edges are the bridge edges
+introduced by the bridge switches from each dual's witness Even Level
+Graph. Each green edge is a bridge of its parity subgraph, so no new cycle
+-- and in particular no odd cycle -- is created; duals $1$ and $2$ coincide
+with their Even Level Graphs and have no added edge.}
 \label{fig:n21-duals}
 \end{figure}