[e-acsl:refman] fix typo

src/plugins/e-acsl/doc/refman/speclang_modern.tex

@@ -308,7 +308,7 @@ undefinitive verdicts (e.g., ``unknown'').
 
 \ifthenelse{\boolean{PrintImplementationRq}}{%
   \begin{notimplementedenv}
-    The following constructs are currently not subsection by the \eacsl plug-in:
+    The following constructs are currently not supported by the \eacsl plug-in:
     \begin{itemize}
     \item built-in function \Length;
     \item comparisons of unions and structures;