docs: update SAML creation for Okta Identity Engine (OIE)

[slavicadev]

Summary
This PR updates the SAML 2.0 application creation guide to account for the UI differences between Okta Classic and Okta Identity Engine (OIE).

The Problem
In Okta Identity Engine (OIE), the "Attribute Statements" section has been removed from the SAML integration wizard. Users following this guide encounter a dead end. As documented in Okta's Help Center, these claims must now be managed via the Sign On tab after the application has been created.

Proposed Changes
Replaced the outdated Attribute Statements step with a blockquote explicitly instructing OIE users to complete the wizard first, then navigate to the Sign On tab to add their custom claims via Okta Expression Language.

[okta-prod-github-app]

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Article	Total score Required:80	Word and phrases (Brand, terms) Preferred: 80	Correctness (Spelling, grammar) Preferred: 80	Clarity (Readability) Preferred: 80	Inclusive language (+ accesibility) Preferred: 80
✅ packages/@okta/vuepress-site/docs/guides/add-private-app/main/saml2/create.md	76	76	100	51

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Depending on the Acrolinx server configuration, the
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[okta-prod-github-app]

Acrolinx score

A minimum Acrolinx Score of 80 is required. The total score is an average of the subscores.
Select Total score to review the Acrolinx scorecard for your article. Try to increase your individual scores, for example: Correctness. Your content will be clearer and more consistent.

Article	Total score Required:80	Word and phrases (Brand, terms) Preferred: 80	Correctness (Spelling, grammar) Preferred: 80	Clarity (Readability) Preferred: 80	Inclusive language (+ accesibility) Preferred: 80
✅ packages/@okta/vuepress-site/docs/guides/add-private-app/main/saml2/create.md	81	87	100	61

Successfully checked 1 of 1 documents.
See summary in Content Analysis Dashboard

Reopen the pull request or push new changes to check again.

Depending on the Acrolinx server configuration, the
links expire after some time and you must have a login for the
Acrolinx server to access them again.