Recent tightening of allowed array-literal syntax broke one test case

in contrib/ltree.  Fix.

Author: tglsfdc

contrib/ltree/expected/ltree.out

@@ -239,7 +239,7 @@ SELECT ''::ltree || 'Top.Child1.Child2'::ltree;
  Top.Child1.Child2
 (1 row)
 
-SELECT lca('{la.2.3,1.2.3.4.5.6,}') IS NULL;
+SELECT lca('{la.2.3,1.2.3.4.5.6,""}') IS NULL;
  ?column? 
 ----------
  t

contrib/ltree/sql/ltree.sql

@@ -47,7 +47,7 @@ SELECT 'Top_0'::ltree || 'Top.Child1.Child2'::ltree;
 SELECT 'Top.Child1.Child2'::ltree || ''::ltree;
 SELECT ''::ltree || 'Top.Child1.Child2'::ltree;
 
-SELECT lca('{la.2.3,1.2.3.4.5.6,}') IS NULL;
+SELECT lca('{la.2.3,1.2.3.4.5.6,""}') IS NULL;
 SELECT lca('{la.2.3,1.2.3.4.5.6}') IS NULL;
 SELECT lca('{1.la.2.3,1.2.3.4.5.6}');
 SELECT lca('{1.2.3,1.2.3.4.5.6}');