CI: Use bot account for backports

[bastelfreak]

Short description

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)

[OpenVoxProjectBot]

Backport failed for 8.x, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin 8.x
git worktree add -d .worktree/backport-472-to-8.x origin/8.x
cd .worktree/backport-472-to-8.x
git switch --create backport-472-to-8.x
git cherry-pick -x 455a567751b5543f30f2153c7b3d1f09ed4a9351