fix: remove stray EOFcat heredoc artifact from SECURITY.md

[akhilesharora]

What does this PR do?

Removes the stray EOFcat SECURITY.md line at the end of SECURITY.md. The text is a heredoc terminator that leaked into the file when PR #410 first added the policy, and it renders verbatim on GitHub as the final line of the security policy page.

$ tail -1 SECURITY.md       # before
EOFcat SECURITY.md
$ tail -1 SECURITY.md       # after
- Report suspicious agent definitions that attempt prompt injection

One line delete. No other changes.

Agent Information (if adding/modifying an agent)

N/A. Doc fix to SECURITY.md.

Checklist

• Follows the agent template structure from CONTRIBUTING.md (N/A, doc fix)
• Includes YAML frontmatter with name, description, color (N/A, doc fix)
• Has concrete code/template examples (for new agents) (N/A, doc fix)
• Tested in real scenarios (tail -1 SECURITY.md before and after)
• Proofread and formatted correctly

Closes #530

[bensl84]

Closing — this is my personal fork (bensl84/agency-agents). The canonical project lives at https://github.com/msitarzewski/agency-agents — please re-open your PR there. Thanks!