SSO: add the missing fields to the okta provider

[dmihai]

What is this feature?

Adding the missing allowSignUp and autoLogin fields to the okta provider in the UI.

Why do we need this feature?

The okta provider was missing some fields in the SSO settings UI.

Who is this feature for?

everybody

Which issue(s) does this PR fix?:

Fixes #

Special notes for your reviewer:

Please check that:

• It works as expected from a user's perspective.
• If this is a pre-GA feature, it is behind a feature toggle.
• The docs are updated, and if this is a notable improvement, it's added to our What's New doc.

[grafana-delivery-bot]

Hello @dmihai!
Backport pull requests need to be either:

• Pull requests which address bugs,
• Urgent fixes which need product approval, in order to get merged,
• Docs changes.

Please, if the current pull request addresses a bug fix, label it with the type/bug label.
If it already has the product approval, please add the product-approved label. For docs changes, please add the type/docs label.
If the pull request modifies CI behaviour, please add the type/ci label.
If none of the above applies, please consider removing the backport label and target the next major/minor release.
Thanks!

[grafana-delivery-bot]

This PR must be merged before a backport PR will be created.