fix typo

Author: vladak

signals.tex

@@ -143,8 +143,8 @@
     \end{itemize}
 \item Example: \example{signals/killing-myself.c}
 \item Using \texttt{0} as \emph{\texttt{sig}} may be used for a simple check for
-the specific process existence, see \example{signals/check-existence.c}.  Not
-signal is sent in that case.
+the specific process existence, see \example{signals/check-existence.c}.
+No signal is sent in that case.
 \end{itemize}
 
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