fix: remove retired sysreport tool from Arm migration agent

[sairamvarmabudharaju]

Pull Request Checklist

• I have read and followed the CONTRIBUTING.md guidelines.
• I have read and followed the guidance for submissions involving paid services.
• The existing agent remains in the correct directory and follows the naming convention.
• The content remains clearly structured and follows the existing format.
• Tested interactively with GitHub Copilot — not run; this is a configuration-only removal.
• Ran npm start — dependency installation was blocked by registry connectivity; CI will verify generation.
• I am targeting the main branch.

---

Description

Removes sysreport_instructions from the Arm migration agent's allowed Arm MCP tools.

Arm MCP no longer exposes this tool, so retaining it could cause the agent to request an unavailable tool. No prompt instructions, Docker configuration, or other tool entries are changed.

---

Type of Contribution

• Update to an existing agent.

---

Additional Notes

• Verified against the current arm/mcp main branch.
• YAML frontmatter parses successfully.
• git diff --check passes.
• LF line endings are preserved.
• The PR contains one commit changing one line in one file.