Actions: Remove labels_template

[tvdeyen]

They do not work as intended

tibdex/backport#97

[github-actions]

The backport to test-branch failed:

The process '/usr/bin/git' failed with exit code 128

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-test-branch test-branch
# Navigate to the new working tree
cd .worktrees/backport-test-branch
# Create a new branch
git switch --create backport-2564-to-test-branch
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 0fa9e081f39a1f3b345ddc18d5b56c10d6b3deeb
# Push it to GitHub
git push --set-upstream origin backport-2564-to-test-branch
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-test-branch

Then, create a pull request where the base branch is test-branch and the compare/head branch is backport-2564-to-test-branch.