Fix admin LDAP sync test

What does this MR do?

Fixes a test that failed in an unrelated MR: https://gitlab.com/gitlab-org/gitlab-qa/-/jobs/303442098

1) Manage LDAP admin sync sets and removes user's admin status
     Failure/Error: login_page.sign_in_using_ldap_credentials(user)
     
     ArgumentError:
       wrong number of arguments (given 1, expected 0; required keyword: user)
     # ./qa/page/main/login.rb:77:in `sign_in_using_ldap_credentials'
     # ./qa/specs/features/ee/browser_ui/1_manage/ldap/admin_ldap_sync_spec.rb:57:in `block (2 levels) in login_with_ldap_admin_user'

Not sure why it passed in the MR when it was changed: !17260 (merged)

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content

/cc @asoborov because you might see this test fail in the nightly pipeline.