Improve description for "Maximum Tokens" setting

If a user tries to remember on more browsers than is configured to be allowed, the token for that user that is next to expire is deleted.

This means it's either:
- If token expiry is refreshed when used: the least recently used token
- If token expiry is fixed based on creation: the oldest created token

https://git.drupalcode.org/project/persistent_login/-/blob/2.x/src/Token...

Hi @knyshuk.vova, @gapple,
I investigated the issue and found that the new token always overrides the most recent one.
I set the maximum token limit to 3, so after the 3rd token is saved, it overrides the latest one (the 3rd token).
I'm attaching the screenshots for your reference.

Please let me know if it looks good to you, and then I'll update the description as well.

@lavanyatalwar can you detail your testing steps, including how you ensured that the browser is requesting a new token on login while the maximum is present in the database?