docs(secure-container): remove outdated performance comparison section

[fengcone]

Summary

• What is changing and why?

Testing

• Not run (explain why) docs only
• Unit tests
• Integration tests
• e2e / manual verification

Breaking Changes

• None
• Yes (describe impact and migration path)

Checklist

• Linked Issue or clearly described motivation
• Added/updated docs (if needed)
• Added/updated tests (if needed)
• Security impact considered
• Backward compatibility considered

[chatgpt-codex-connector]

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[hittyt]

LGTM