Ruby: Explain difference between flow tests

The type-tracking flow tests document the difference in sensitivity
between type-tracking and dataflow, so failures in that test are
expected.

Author: hmac

ruby/ql/test/library-tests/dataflow/array-flow/type-tracking-array-flow.ql

@@ -1 +1,6 @@
+// This test flags any difference in flow between the type-tracking and dataflow
+// libraries. New results in this query do not necessarily indicate a problem,
+// only that type-tracking cannot follow the flow in your test. If the dataflow
+// test (`array-flow.ql`) shows no failures, then that may be sufficient
+// (depending on your use case).
 import TestUtilities.InlineTypeTrackingFlowTest

ruby/ql/test/library-tests/dataflow/hash-flow/type-tracking-hash-flow.ql

@@ -1 +1,6 @@
+// This test flags any difference in flow between the type-tracking and dataflow
+// libraries. New results in this query do not necessarily indicate a problem,
+// only that type-tracking cannot follow the flow in your test. If the dataflow
+// test (`hash-flow.ql`) shows no failures, then that may be sufficient
+// (depending on your use case).
 import TestUtilities.InlineTypeTrackingFlowTest