doc: Use '@lisp' for 'options->transformation' example.

* doc/guix.texi (Defining Package Variants): Use @lisp for
'options->transformation' example.

diff --git a/doc/guix.texi b/doc/guix.texi
index 3255eba..a20e54f 100644 (file)
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -6919,10 +6919,10 @@ Return a procedure that, when passed an object to build (package,
 derivation, etc.), applies the transformations specified by @var{opts} and returns
 the resulting objects.  @var{opts} must be a list of symbol/string pairs such as:
 
-@example
+@lisp
 ((with-branch . "guile-gcrypt=master")
  (without-tests . "libgcrypt"))
-@end example
+@end lisp
 
 Each symbol names a transformation and the corresponding string is an argument
 to that transformation.