Update error message copy when maximum number of users reached per license

Problem to solve

Following up from https://github.com/gitpod-io/gitpod/pull/11768#discussion_r934903448, the current message shown when the maximum number of users reached per license has the following issues:

1. It's using an error prefix unnecessarily.
2. It's not clear whether the user actually sign up or not.

Error: Maximum number of users permitted by the license exceeded

CURRENT

Proposal

Update error message copy when maximum number of users reached per license, with a simpler copy but also better structure using bolder font weight for the first sentence.

Seems like the error is also coming from the backend, cross-posting in case this makes it more challenging to come up with the bolder sentence:

https://github.com/gitpod-io/gitpod/blob/ca802d2e7e8dae9b44425f3b65104654cb9fc41c/components/server/ee/src/user/user-service.ts#L90

For example:

Maximum number of users reached. We could not sign you in because this instance has reached the maximum number of allowed users.

See also relevant discussion (internal). Cc @lucasvaltl @geropl @AlexTugarev

Start with components/server/ee/src/user/user-service.ts around line 90 and read the linked discussion for the current error wording. Trace where that message is presented to users so the first sentence can use bolder text. Done means the unnecessary error prefix is removed and the message clearly explains that sign-in could not proceed because the license user limit was reached.