SF bug #987486: fix typo.

Doc/lib/libcgi.tex

@@ -241,7 +241,7 @@ A more convenient approach is to use the methods \method{getfirst()}
 and \method{getlist()} provided by this higher level interface.
 
 \begin{methoddesc}[FieldStorage]{getfirst}{name\optional{, default}}
-  Thin method always returns only one value associated with form field
+  This method always returns only one value associated with form field
   \var{name}.  The method returns only the first value in case that
   more values were posted under such name.  Please note that the order
   in which the values are received may vary from browser to browser