fix wording

Author: Vladimir Kotal

threads.tex

@@ -1249,7 +1249,7 @@
 \begin{itemize}
 \item \emph{Interesting property}: if a thread waiting on a read-write lock
 receives a signal, the signal handler will be invoked and then it will
-transparently continue waiting, i.e. there will be no error \texttt{EINTR}.
+transparently continue waiting, i.e. there will be no \texttt{EINTR} error.
 The same is true for mutexes and condition variables.
 \end{itemize}