Resolve "Admins should be able to set the new user sign up cap at a value higher than the licensed user count"

What does this MR do and why?

This MR removes the restriction on the user signups cap setting that prevents admins from raising the cap higher than the licensed user count on the instance.

Screenshots or screen recordings

Before	After

How to set up and validate locally

Prerequisites:

• EE instance with an active license

Steps:

1. Navigate to the Admin section, then Settings -> General
2. Expand Sign-up Restrictions
3. In the User cap field, enter an integer value greater than the licensed user count on the instance
4. Click Save

Expected behavior:

• The user cap setting is saved successfully

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Closes #348480 (closed)