fix typo

base/doc/ltnews41.tex

@@ -375,7 +375,7 @@ \subsection{Prevent \texttt{cmd} hook from defining an undefined command}
 
 Using \verb=AddToHook{cmd/FOO/...}= when the command \cs{FOO} was
 undefined resulted in the command becoming \cs{relax}. Thus, if used,
-it no longer raised and \enquote{Undefined csname} error but silently
+it no longer raised an \enquote{Undefined csname} error but silently
 did nothing. This behavior has been corrected and if the command
 \cs{FOO} isn't defined later, e.g., in a package, it now raises an
 error if it is used in the document.