Python: Update isSequence() and isMapping() for Python 3.8

Author: RasmusWL

python/ql/test/library-tests/PointsTo/class_properties/ClassValues.expected

@@ -1,8 +1,8 @@
-| mapping | builtin-class collections.defaultdict |
-| mapping | builtin-class dict |
 | neither sequence nor mapping | builtin-class set |
 | sequence | builtin-class bytes |
 | sequence | builtin-class collections.OrderedDict |
+| sequence | builtin-class collections.defaultdict |
+| sequence | builtin-class dict |
 | sequence | builtin-class list |
 | sequence | builtin-class str |
 | sequence | builtin-class tuple |