[TASK] Update mod.SHARED.colPos_list

[linawolf]

The standard backend layout has only
one column since at least 8.7. According to the code in the Core the default value is empty.

Update the example removing outdated screenshots and use a backend layout defined via page TSconfig.

Releases: main, 13.4, 12.4

[github-actions]

The backport to 12.4 failed:

The process '/usr/bin/git' failed with exit code 1

stderr

error: could not apply 9c8e596... [TASK] Update mod.SHARED.colPos_list
hint: After resolving the conflicts, mark them with
hint: "git add/rm <pathspec>", then run
hint: "git cherry-pick --continue".
hint: You can instead skip this commit with "git cherry-pick --skip".
hint: To abort and get back to the state before "git cherry-pick",
hint: run "git cherry-pick --abort".
hint: Disable this message with "git config advice.mergeConflict false"

stdout

CONFLICT (modify/delete): Documentation/PageTsconfig/Mod/WebLayout/_BackendLayout.tsconfig deleted in HEAD and modified in 9c8e596 ([TASK] Update mod.SHARED.colPos_list).  Version 9c8e596 ([TASK] Update mod.SHARED.colPos_list) of Documentation/PageTsconfig/Mod/WebLayout/_BackendLayout.tsconfig left in tree.

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-12.4 12.4
# Navigate to the new working tree
cd .worktrees/backport-12.4
# Create a new branch
git switch --create backport-566-to-12.4
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick 9c8e596fef70cca863d1b5baa69ac0b387bc47cb
# Push it to GitHub
git push --set-upstream origin backport-566-to-12.4
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-12.4

Then, create a pull request where the base branch is 12.4 and the compare/head branch is backport-566-to-12.4.