Revise individual developer account registration steps

[chetnadas]

Updated the steps for opening an individual developer account, including changes to the registration process and additional notes for users.

[prmerger-automator]

@chetnadas : Thanks for your contribution! The author(s) and reviewer(s) have been notified to review your proposed change.

[learn-build-service-prod]

Learn Build status updates of commit aeb170f:

⚠️ Validation status: warnings

File	Status	Preview URL	Details
hub/apps/publish/partner-center/open-a-developer-account.md	⚠️Warning		Details

hub/apps/publish/partner-center/open-a-developer-account.md

• Line 29, Column 1: [Warning: file-not-found - See documentation] Invalid file link: 'images/new-website.png'.
• Line 37, Column 1: [Warning: file-not-found - See documentation] Invalid file link: 'images/choose-account.png'.
• Line 57, Column 1: [Warning: file-not-found - See documentation] Invalid file link: 'images/apps-games-overview-page.png'.

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.

[learn-build-service-prod]

Learn Build status updates of commit 62616e2:

⚠️ Validation status: warnings

File	Status	Preview URL	Details
hub/apps/publish/partner-center/open-a-developer-account.md	⚠️Warning		Details

hub/apps/publish/partner-center/open-a-developer-account.md

• Line 29, Column 1: [Warning: file-not-found - See documentation] Invalid file link: './images/new-website.png'.
• Line 37, Column 1: [Warning: file-not-found - See documentation] Invalid file link: './images/choose-account.png'.
• Line 57, Column 1: [Warning: file-not-found - See documentation] Invalid file link: './images/apps-games-overview-page.png'.

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.

[learn-build-service-prod]

Learn Build status updates of commit 7197e7b:

✅ Validation status: passed

File	Status	Preview URL	Details
hub/apps/publish/partner-center/open-a-developer-account.md	✅Succeeded

For more details, please refer to the build report.

[prmerger-automator]

PRMerger Results

Issue	Description
File Change Percent	This PR contains file(s) with more than 30% file change.