tools: enable no-return-await lint rule

Enable lint rule that prohibits unnecessary use of `await` with
`return`.

PR-URL: #17265
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>

.eslintrc.yaml

@@ -66,6 +66,7 @@ rules:
       message: __defineGetter__ is deprecated.
     - property: __defineSetter__
       message: __defineSetter__ is deprecated.
+  no-return-await: error
   no-self-assign: error
   no-throw-literal: error
   no-unused-labels: error