Docs: Clarify "seats owed" and "users in/over subscription"

• Start this issue's title with Docs: or Docs feedback:.

Problem to solve

The number of users over subscription is calculated in the same way for .com and self-managed, but the docs explain the process with different terms:

• .com: "seats owed"
• SM: "users over subscription". Also "users in subscription" and "users in license" are used interchangeably, which is confusing.

Proposal

Align the sections related to users over subscription on .com and SM.

Who can address the issue

PM and TW

Other links/references