Adding explicitly requirement to set context of subscription

[GomanovNA]

If we can update this document explicitly defining that subscription for each context should be set in a certain way then it might help in future to have less problems. Had a ticket with Support team and even they couldn't tell me immediately what's the problem. And the problem was that I set context as az cli way and was registering feature via azure powershell and there was no error or hint to tell me that I'm enabling feature for wrong subscription. Ticket is RE: Cant create vm encryption at host - TrackingID#2411200050000262

[prmerger-automator]

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

[learn-build-service-prod]

Learn Build status updates of commit 47b7475:

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articles/virtual-machines/disks-enable-host-based-encryption-portal.md	✅Succeeded

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[Jak-MS]

@roygara
Can you review the proposed changes?

Important: When the changes are ready for publication, adding a #sign-off comment is the best way to signal that the PR is ready for the review team to merge.

#label:"aq-pr-triaged"
@MicrosoftDocs/public-repo-pr-review-team

[roygara]

@GomanovNA Thanks for helping to improve our docs, we appreciate it! Overall this looks good, just two changes then it's good to go. :)

[learn-build-service-prod]

Learn Build status updates of commit 7cd47b7:

✅ Validation status: passed

File	Status	Preview URL	Details
articles/virtual-machines/disks-enable-host-based-encryption-portal.md	✅Succeeded

For more details, please refer to the build report.

For any questions, please:

• Try searching the learn.microsoft.com contributor guides
• Post your question in the Learn support channel

[Court72]

@roygara, For convenience, I committed your suggestions and merged this PR based on your approval. If this article requires further changes, please open a separate pull request. Thanks!