Yearly review of labels on issues

[BillWagner]

Describe the issue or suggestion

It's time for the yearly review of labels we use.

• Determine which labels are still in use
• Remove unused labels

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Associated WorkItem - 360308

[BillWagner]

I don't list any of the /svc or /subsvc labels here. That should be covered under a second review. I've already deleted any */prod and */tech labels.

• accessibility: There are no current issues, and it hasn't been used since 2022
• area-System.Text.Json: 1 open issue, created in 2023. 9 closed issues, last active in March 2023
• azure-sdk-shipit: Doesn't seem to be used
• 📑 Information Architecture: historical?
• broken-link: Used only once in the last year
• 🏗️ Try.NET upgrade needed: The upgrade has taken place, so these samples should work now.
• bulk-changes: Hasn't been used in years.
• by design: The label isn't used (even though we close issues for this reason)
• 🏁 Release: .NET Framework 4.8.1: Do we need this data?
• 🏁 Release: .NET 5: No longer supported
• 🏁 Release: .NET 6: No longer supported. This leaves the labels for .NET 7, .NET 8, .NET 9, and .NET 10.)
• 🚧 Hold for related PR: How is this different then "blocked"?!
• doc-bug: No longer tracked
• doc-enhancement: No longer tracked
• doc-idea: No longer tracked
• docs-experience: These are now reported internally.
• duplicate: Not sure if we use the label.
• external: Not Used
• migration-fixes: Was for issues related to the migration from MSDN. Not used in years.
• mvp-docs-sprint: Was some time in the past.
• .NET: Unused
• okr-health: No longer tracked.
• Pri0, Pri1, Pri2, Pri3: These were added based on page view data. If we reimplement it, we'll use a different label.
• product-feedback: Usually transferred to the product team repos.
• product-question: Not tracked.
• resolved-by-customer: Not added now. If we wanted this, we could apply it when the OP closes an issue. I doubt it's worth it.
• sample-code: Unused
• seo: Unused
• ✨ 1st-time docs contributor!: Unused
• 🌟 What's New: These aren't issues on the what's new in docs page, but rather new features in .NET that we're missing. This hasn't been used in several releases.
• style-guide: Not Used
• support-request: Not Used
• test-issue: Is this used?
• training-module: Do those get used in this repo?
• vendor-project: It's used at times, but not regularly.
• video-content: Not used.
• won't fix: Should we just close these?

The labels above with strikethrough are still in use (per comments with 👍 below). Those won't be removed.

[CamSoper]

• training-module: Do those get used in this repo?
• video-content: Not used.

I created these, but as I am now tracking this work in AzDO, they can be retired here.

[gewarren]

🚧 Hold for related PR: How is this different then "blocked"?

I'd like to keep it and have used it recently. PRs could be blocked for reasons other than waiting for another PR, so I think we need both.

docs-experience: These are now reported internally.

It would still be nice to tag these site issues that we can't do anything about and can't transfer automagically.