fix translation

Author: Vladimir Kotal

threads.tex

@@ -1333,7 +1333,7 @@
 requires much more invention.
 \item The reentrant functions are also the only usable functions in
 signal handlers.
-\item These days thread-safe usually means reentrantní, however it does not
+\item These days thread-safe usually means reentrant, however it does not
 hurt to know the difference.
 \item For more on library locking see also page \pageref{MUTEXES2}.
 \item There exists a number of functions that can be thread-safe, however