Eslint rule: consider switching consistent-this to "that"

Our rule for consistent-this is set to "self": https://framagit.org/kresusapp/kresus/-/blob/master/.eslintrc.yml#L328.

Example: https://framagit.org/kresusapp/kresus/-/blob/master/server/lib/async-queue.js#L50

I find it confusing because in a browser self is already a defined variable with a meaning: https://developer.mozilla.org/fr/docs/Web/API/Window/self.

I'd prefer using that instead.