Adds a section on unsupported keys to troubleshoot-tde.md

[iamjustsam]

Adds a section on unsupported keys. Using an unsupported key will throw an InternalServerError without further information.

[iamjustsam]

@microsoft-github-policy-service agree

[prmerger-automator]

@iamjustsam : 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 8eeb8f5:

✅ Validation status: passed

File	Status	Preview URL	Details
docs/relational-databases/security/encryption/troubleshoot-tde.md	✅Succeeded

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[v-regandowner]

@rwestMSFT - 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

[VanMSFT]

Hi @Pietervanhove - Can you please review to see if this is an appropriate addition the doc? Thanks!

#assign:Pietervanhove

[Pietervanhove]

It might be a good idea to add this, but I'm not sure if the error message "500 InternalServerError - An unexpected error occured while processing the request." is only related to a wrong key format. I'll need to double check with engineering.