Fix markup

Doc/lib/libgettext.tex

@@ -319,7 +319,7 @@ To facilitate plural forms, the methods \method{ngettext} and
 \method{ungettext} are overridden as well.
 
 \begin{methoddesc}[GNUTranslations]{__init__}{
-    \optional{fp\optional{, coerce}}
+    \optional{fp\optional{, coerce}}}
 Constructs and parses a translation catalog in GNU gettext format.
 \var{fp} is passed to the base class (\class{NullTranslations})
 constructor.  \var{coerce} is a flag specifying whether message ids