fixed typo [ci skip]

base/ltsect.dtx

@@ -784,7 +784,7 @@
 \def\addcontentsline#1#2#3{%
   \addtocontents{#1}{\protect\contentsline{#2}{#3}{\thepage}%
 %    \end{macrocode}
-%    We add \cs{protected@file@percent} at the end which is turned om
+%    We add \cs{protected@file@percent} at the end which is turned inside
 %   \cs{@writefile} into a percent character to mask the newline after
 %   the closing argument brace.
 %    \begin{macrocode}