fix test case

nullaway/src/test/resources/com/uber/nullaway/testdata/NullAwayStreamSupportPositiveCases.java

@@ -191,7 +191,8 @@ private Stream<T> test1(Stream<T> stream) {
 
     private Stream<T> test2(Stream<T> stream) {
       Preconditions.checkNotNull(ref);
-      // BUG: Diagnostic contains: dereferenced expression ref is @Nullable
+      // no error since we propagate nullability facts to stream callbacks, which
+      // in sane code are invoked soon after the stream is
       return stream.filter(s -> ref.equals(s));
     }
   }