Remove metadata from ConcPoly example

doc/libraries_ref_guide/LibDoc/Prelude.tex

@@ -7073,24 +7073,20 @@ \subsubsection{Representation types}
    struct Foo_x =
      val :: a -> a
 
-   instance Generic Foo
-     (Meta (MetaData "Foo" "Example" () 1)
-      (Meta (MetaConsNamed "Foo" 0 2)
-       (Meta (MetaField "x" 0) (ConcPoly Foo_x),
-        Meta (MetaField "y" 1) (Conc (Int 8))))) where
-     from a =
-       Meta (Meta (Meta (ConcPoly (Foo_x { val = a.x; })), Meta (Conc a.y)))
-     to (Meta (Meta ((Meta (ConcPoly x)), (Meta (Conc y))))) =
-       Test.Foo { x = x.val; y = y; }
+   instance Generic Foo (ConcPoly Foo_x, Conc (Int 8))) where
+     from a = (ConcPoly (Foo_x { val = a.x; }), Conc a.y)
+     to (ConcPoly x, Conc y) = Foo { x = x.val; y = y; }
 \end{libverbatim}
 
 Users can omit an instance for \te{ConcPoly} to not support higher-rank data,
 or define some useful default behavior.
+For example, the \te{CShow} library defines an instance for ConcPoly
+to return a placeholder string for higher-rank fields.
 
 \subsubsection{Metadata types}
 
 The following types are used to represent metadata in generic representations.
-Note that these only appear as at the type level tagging a \te{Meta} type;
+Note that these only appear at the type level tagging a \te{Meta} type;
 values of these types are not constructed.
 
 \begin{center}