Fix CQL2 parser for BETWEEN operator (#251)

* Fix CQL2 parser for BETWEEN operator

* Update the test

Author: drnextgis

src/pgstac/sql/002b_cql.sql

@@ -344,8 +344,8 @@ BEGIN
     IF op = 'between' THEN
         args = jsonb_build_array(
             args->0,
-            args->1->0,
-            args->1->1
+            args->1,
+            args->2
         );
     END IF;
 

src/pgstac/tests/pgtap/004_search.sql

@@ -401,7 +401,7 @@ SELECT results_eq($$
             "op": "between",
             "args": [
             { "property": "eo:cloud_cover" },
-            [ 0, 50 ]
+            0, 50
             ]
         }
     }