list-packages: remove deprecated "height" attribute on "td" element.

See http://www.w3.org/TR/html5-diff/#obsolete-attributes for more information.

* build-aux/list-packages.html(package-sxml)[description-id]: remove "height"
  attribute for "td" elements.

build-aux/list-packages.scm

@@ -103,7 +103,7 @@ exec guile -l "$0"                              \
                   (title "Link to the Guix package source code"))
                ,(package-name package) " "
                ,(package-version package)))
-        (td (@ (colspan "2") (height "0"))
+        (td (@ (colspan "2"))
             (a (@ (href "javascript:void(0)")
                   (title "show/hide package description")
                   (onClick ,(format #f "javascript:show_hide('~a')"