feat: add unnecessary await unicorn rule [no issue]

[keabard]

Context

https://github.com/sindresorhus/eslint-plugin-unicorn/blob/main/docs/rules/no-unnecessary-await.md

Solution

We add it

[reviewflow]

Options:

• 🔜 automerge: Automatically merge when this PR is ready and has no failed statuses. When the repository requires branches to be up to date before merging, it merges default branch, with a queue per repo to prevent multiple merges when several PRs are ready. A fail job prevents the merge.
• 🚦 skip-ci: Add [skip ci] on merge commit when merge is done with autoMerge.
• ♻️ Automatically delete the branch after this PR is merged. (⚠️ Legacy Option: Delete branch with Github Setting)

Actions:

• 🐛 Force updating reviewflow checks for this PR. Use this to try to fix reviewflow checks that are still missing/pending, which might happen if webhook failed or something bad happened when reviewflow tried to send the status check to github.
• 🔄 update branch: Merge base branch in this PR's branch. Only works if merging is possible without conflicts.

[christophehurpeau]

#426