Fix unused async in spec/frontend/[r-u]*

What does this MR do and why?

Fix async functions with no await in some jest runner tests.

Implements 3/4 of #406588 (closed)

Related: #397674 (closed), gitlab-org/frontend/eslint-plugin#13

Screenshots or screen recordings

NA

How to set up and validate locally

You may run these commands to verify:

$ yarn eslint --no-error-on-unmatched-pattern --rule 'require-await: error' spec/frontend/[r-u]*