Remove grace period from license expiration check

[rjernst]

License expiration checking currently has a 7 day grace period. When a
license expires, the licensing code acts as if it is not yet expired.
This was originally intended to protect users who may accidentally end up
letting their license expire from the pain of their licensed features
ceasing to work. However, the grace period effectively shifts the
license expiration by a week, resulting in confusion since the actual
license expiration date is not accurate. It also is less of a concern
now as not only do we emit several warnings for upcoming license
expiration, but the new license can be downloaded and installed quickly
by the user through the support portal.

This commit removes the license grace period altogether.

[elasticmachine]

Pinging @elastic/es-security (Team:Security)

[rjernst]

Note that I have marked this as >breaking even though it is not actually breaking, since it is not related to any API a user uses. Unfortunately I don't see an existing category label that can describe such a behavior change which doesn't actually affect users, but is still included in the release notes.

[bytebilly]

Thanks @rjernst, I agree it is not a breaking change for users as the grace period is not something they know/rely on.

[mark-vieira]

@elasticmachine update branch

[jasontedor]

LGTM.

[williamrandolph]

I will put this under "Enhancements" in the release notes so that it's not the first thing that users see.