JS: Move identityFunctionStep back into CachedSteps module

javascript/ql/lib/semmle/javascript/dataflow/internal/FlowSteps.qll

@@ -520,9 +520,6 @@ private module CachedSteps {
   predicate receiverPropWrite(Function f, string prop, DataFlow::Node rhs) {
     DataFlow::thisNode(f).hasPropertyWrite(prop, rhs)
   }
-}
-
-import CachedSteps
 
   /**
    * Holds if there is a step from `pred` to `succ` through a call to an identity function.
@@ -536,6 +533,9 @@ predicate identityFunctionStep(DataFlow::Node pred, DataFlow::CallNode succ) {
       pred = succ.getArgument(0)
     )
   }
+}
+
+import CachedSteps
 
 /**
  * A utility class that is equivalent to `boolean` but does not require type joining.