revert caching of some large predicates that caused the DB size to increase too much

python/ql/lib/semmle/python/Flow.qll

@@ -194,9 +194,7 @@ class ControlFlowNode extends @py_flow_node {
   BasicBlock getBasicBlock() { result.contains(this) }
 
   /** Gets the scope containing this flow node */
-  cached
   Scope getScope() {
-    Stages::AST::ref() and
     if this.getNode() instanceof Scope
     then
       /* Entry or exit node */