Update developer program details and add billing requirements

[akagarwa-msft]

Updated the date for the Microsoft 365 developer program and added a billing account requirement section with detailed instructions.

[learn-build-service-prod]

PoliCheck Scan Report

The following report lists PoliCheck issues in PR files. Before you merge the PR, you must fix all severity-1 and severity-2 issues. The AI Review Details column lists suggestions for either removing or replacing the terms. If you find a false positive result, mention it in a PR comment and include this text: #policheck-false-positive. This feedback helps reduce false positives in future scans.

✅ No issues found

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[learn-build-service-prod]

Learn Build status updates of commit 9a301cc:

💡 Validation status: suggestions

File	Status	Preview URL	Details
docs/microsoft-365-developer-program-get-started.md	💡Suggestion	View	Details

docs/microsoft-365-developer-program-get-started.md

• Line 230, Column 137: [Suggestion: other-site-link-broken - See documentation] Link 'https://developer.microsoft.com/microsoft-365/support' points to a page that doesn't exist. Check the path or URL and update the link.
• Line 238, Column 155: [Suggestion: other-site-link-broken - See documentation] Link 'https://developer.microsoft.com/microsoft-365/support' points to a page that doesn't exist. Check the path or URL and update the link.

For more details, please refer to the build report.

Note: Your PR may contain errors or warnings or suggestions unrelated to the files you changed. This happens when external dependencies like GitHub alias, Microsoft alias, cross repo links are updated. Please use these instructions to resolve them.