Fix accidentally repeated proof list

spec/doc.tex

@@ -1437,13 +1437,6 @@ The following lists all rules of {\formatName}.
 
 \input{rule_list}
 
-\section{List of Proof Rules}
-\label{sec:rules}
-
-The following lists all rules of {\formatName}.
-
-\input{rule_list}
-
 \section{Changelog}
 \label{sec:changelog}