remove use of .getAlocalSource() i custom load/store test

Author: erik-krogh

javascript/ql/test/library-tests/CustomLoadStoreSteps/test.ql

@@ -13,7 +13,11 @@ class Configuration extends TaintTracking::Configuration {
 
   // When the source code states that "foo" is being read, "bar" is additionally being read.
   override predicate isAdditionalLoadStep(DataFlow::Node pred, DataFlow::Node succ, string prop) {
-    pred.(DataFlow::SourceNode).getAPropertyRead("foo") = succ and prop = "bar"
+    exists(DataFlow::PropRead read | read = succ | 
+      read.getBase() = pred and
+      read.getPropertyName() = "foo"
+    ) and
+    prop = "bar"
   }
 }