Update test case for lifted GADT type rendering

The parsing of these seems to have been fixed by GHC folk and it now
renders differently. IMHO it now renders in a better way so I'm updating
the test to reflect this.

html-test/ref/AdvanceTypes.html

@@ -63,7 +63,7 @@ window.onload = function () {pageLoad();setSynopsis("mini_AdvanceTypes.html");};
 		  >Nil</a
 		  > ::  <a href=""
 		  >Pattern</a
-		  > `[]`</td
+		  > []</td
 		><td class="doc empty"
 		>&nbsp;</td
 		></tr