fix typo

base/doc/tlc3.err

@@ -702,8 +702,8 @@ Add sentence: The command \verb+\textcquote+ is used in Example 16-5-50 on page
 Replace the whole paragraph with:\\
 For the same reason \texttt{soul} was unable to cope with UTF-8 input
 characters if they are internally represented by several bytes. If you
-used such characters, you had to load \texttt{soulutf8} (by by Heiko Oberdiek)
-instead of soul — since 2023 both packages are equivalent, thus \texttt{soul}
+used such characters, you had to load \texttt{soulutf8} (by Heiko Oberdiek)
+instead of \texttt{soul} — since 2023 both packages are equivalent, thus \texttt{soul}
 can always be used.
 
 \CHAPTER{Chapter 4 --- Basic Formatting Tools -- Larger \ldots}