Python: Fix query tests

Mostly just adding `private import LegacyPointsTo`. Sometimes getting
rid of other imports that are superceded by that module.

python/ql/src/Functions/OverlyComplexDelMethod.ql

@@ -12,6 +12,7 @@
  */
 
 import python
+private import LegacyPointsTo
 
 from FunctionValue method
 where