dtx: fix doc PDF

Author: xqms

graphicscache.dtx

@@ -496,7 +496,7 @@
 %    \begin{macrocode}
 \newcommand{\graphicscache@work}{%
 %    \end{macrocode}
-% Parse \ifgraphicscache@render and \graphicscache@inhibit
+% Parse |\ifgraphicscache@render| and |\graphicscache@inhibit|
 %    \begin{macrocode}
   \ifdefined\graphicscache@inhibit
     \graphicscache@dorenderfalse