Fix section header in OpenVoxDB 8.13.0 notes

[Sharpie]

Short description

I was a little fast on the copy + paste and accidentally duplicated the Security Issues Resolved in 8.14.0 header. This commit corrects the version to the intended 8.13.0.

Checklist

I have:

• read the CONTRIBUTING.md document
• read and accepted the Developer Certificate of Origin document and added a Signed-off-by annotation to each of my commits
• read and accepted the AI Policy document and added Generated-by or Assisted-by annotations to each of my commits created with the help of an AI agent
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)