[skip ci] Doc: update the Apache Security email address

[tuhaihe]

Fixes #ISSUE_Number

What does this PR do?

Correct the format of the Apache Security email address in markdown, allowing community members to click it directly to send an email.

Type of Change

• [ ] Bug fix (non-breaking change)
• [ ] New feature (non-breaking change)
• [ ] Breaking change (fix or feature with breaking changes)
• [x] Documentation update

Breaking Changes

Test Plan

• [ ] Unit tests added/updated
• [ ] Integration tests added/updated
• [ ] Passed make installcheck
• [ ] Passed make -C src/test installcheck-cbdb-parallel

Impact

Performance:

User-facing changes:

Dependencies:

Checklist

• [x] Followed contribution guide
• [x] Added/updated documentation
• [x] Reviewed code for security implications
• [x] Requested review from cloudberry committers

Additional Context

⚠️ To skip CI: Add [skip ci] to your PR title. Only use when necessary! ⚠️

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