Adjust no-loops-in-noSuchMethod example

Author: eernstg

specification/dartLangSpec.tex

@@ -3429,7 +3429,7 @@ \subsubsection{The Method \code{noSuchMethod}}
 
 \begin{dartCode}
 \CLASS{} A \{
-  noSuchMethod(\COVARIANT{} Null n) => n;
+  noSuchMethod(\COVARIANT{} Never n) => n;
 \}
 \\
 \VOID{} main() \{