Mark existing Project Bot Users as confirmed

What does this MR do?

For #219539 (closed), and is a continuation of the fix made in !35498 (merged).

Creating a project access token also creates a Project Bot user internally, and these users have to be confirmed by default, else the PATs of these users will not work after the grace period (during which unconfirmed users can still sign in).

Query

SELECT "users".* FROM "users" WHERE "users"."user_type" = 6 AND "users"."confirmed_at" IS NULL

Explain

Since this feature is still not available on GitLab.com and only available on self-managed instances, the above query returns 0 rows on GitLab.com database.

Hence, this query will only be applicable for self-managed instances.

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team