Editorial: mark a note step as a note (#3026)

spec.html

@@ -45179,7 +45179,7 @@ <h1>
             1. Assert: If we return here, the generator either threw an exception or performed either an implicit or explicit return.
             1. Remove _acGenContext_ from the execution context stack and restore the execution context that is at the top of the execution context stack as the running execution context.
             1. Set _acGenerator_.[[GeneratorState]] to ~completed~.
-            1. Once a generator enters the ~completed~ state it never leaves it and its associated execution context is never resumed. Any execution state associated with _acGenerator_ can be discarded at this point.
+            1. NOTE: Once a generator enters the ~completed~ state it never leaves it and its associated execution context is never resumed. Any execution state associated with _acGenerator_ can be discarded at this point.
             1. If _result_.[[Type]] is ~normal~, let _resultValue_ be *undefined*.
             1. Else if _result_.[[Type]] is ~return~, let _resultValue_ be _result_.[[Value]].
             1. Else,