User's Guide: Fix compiler plugin example (#9641, #7682)

The previous fix was incorrectly eta-reduced.

docs/users_guide/extending_ghc.xml

@@ -226,8 +226,8 @@ install _ todo = do
   return (CoreDoPluginPass "Say name" pass : todo)
 
 pass :: ModGuts -> CoreM ModGuts
-pass = do dflags <- getDynFlags
-          bindsOnlyPass (mapM (printBind dflags))
+pass guts = do dflags <- getDynFlags
+               bindsOnlyPass (mapM (printBind dflags)) guts
   where printBind :: DynFlags -> CoreBind -> CoreM CoreBind
         printBind dflags bndr@(NonRec b _) = do
           putMsgS $ "Non-recursive binding named " ++ showSDoc dflags (ppr b)