docs(vscode): fix stale Msty provider reference link

[santhiprakash]

Description

The Msty provider entry in extensions/vscode/config_schema.json linked to https://continue.dev/docs/reference/Model%20Providers/Msty, which 404s after the docs migration to docs.continue.dev and because the docs site is case-sensitive on provider slugs.

Updated the Reference link to https://docs.continue.dev/reference/Model%20Providers/msty, matching the other provider links in the same file.

Self-sourced docs drift fix.

Problem

• Old URL (continue.dev/docs/.../Msty) → HTTP 404
• Correct URL (docs.continue.dev/.../msty) → HTTP 200 with Msty provider docs

Triage / Root cause

config_schema.json line 269 still used the pre-migration domain and capitalized Msty slug from the original provider PR (#916). The docs site moved in #13004 and paths are case-sensitive.

Fix

• Replace the Msty provider Reference URL with the current docs domain and lowercase slug.

Verification

• curl -o /dev/null -w '%{http_code}' -L → old URL 404, new URL 200
• python3 -m json.tool extensions/vscode/config_schema.json → valid JSON
• rg 'continue.dev/docs' → no remaining occurrences repo-wide

Notes / Risks

• Docs-only, one-line change in generated schema text.
• No open or merged PR duplicates found for this path.

Checklist

• I've read the contributing guide
• The relevant docs, if any, have been updated or created
• The relevant tests, if any, have been updated or created (not applicable — docs link only)

Tests

Not applicable — documentation link correction only.

[santhiprakash]

I have read the CLA Document and I hereby sign the CLA