Update Datadog plugin repository to datadog-labs/copilot-plugin

[jfree]

Summary

• Datadog renamed their repo from datadog-labs/vscode-plugin to datadog-labs/copilot-plugin (standard GitHub rename so there's a redirect in place from vscode-plugin -> copilot-plugin)
• Updated the source.repo reference in .github/plugin/marketplace.json and plugins/external.json to match

Test plan

• Verify marketplace generation picks up the new repo reference without errors

[github-actions]

✅ External plugin PR checks passed

• Changed entries detected: 1
• Workflow state label: ready-for-review

Per-plugin quality summary

Plugin	vally lint	install smoke test	overall	source tree
datadog	pass	pass	pass	ae77972f050575c0e41b690ccc484aa0a287e9c8

• datadog: vally-lint=pass, install-smoke=pass, overall=pass

[Copilot]

Pull request overview

Updates the Datadog external plugin metadata to reflect Datadog’s repository rename from datadog-labs/vscode-plugin to datadog-labs/copilot-plugin, ensuring the marketplace and external plugin registry point at the correct upstream source.

Changes:

• Updated Datadog repository URL in plugins/external.json.
• Updated Datadog source.repo in plugins/external.json.
• Updated the corresponding Datadog repository and source.repo entries in the generated .github/plugin/marketplace.json.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
plugins/external.json	Updates Datadog external plugin metadata to reference the renamed upstream repository.
.github/plugin/marketplace.json	Mirrors the Datadog repository/source update in the marketplace output.

[github-actions]

🔒 PR Risk Scan Results

Scanned 2 changed file(s).

Severity	Count
🔴 High	0
🟠 Medium	0
ℹ️ Info	0

✅ No matching risk patterns were detected in changed files.

This is an automated soft-gate report. Findings indicate review targets and do not block merge by themselves.