[DOCS] Remove outdated paragraph

[FlyKasual]

There is no necessity anymore for user functions to be prepended with user_ anymore, so that confusing and vague sentence can be removed.

[linawolf]

Thanks a lot and congratulations to your first doc edit ;)

[github-actions]

The backport to 13.4 failed:

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

stderr

The previous cherry-pick is now empty, possibly due to conflict resolution.
If you wish to commit it anyway, use:

    git commit --allow-empty

Otherwise, please use 'git cherry-pick --skip'

stdout

On branch backport-1581-to-13.4
You are currently cherry-picking commit c4caee32.
  (all conflicts fixed: run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

nothing to commit, working tree clean

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-13.4 13.4
# Navigate to the new working tree
cd .worktrees/backport-13.4
# Create a new branch
git switch --create backport-1581-to-13.4
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick c4caee32c7799edc3117c958675675f8f4fd8eaa
# Push it to GitHub
git push --set-upstream origin backport-1581-to-13.4
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-13.4

Then, create a pull request where the base branch is 13.4 and the compare/head branch is backport-1581-to-13.4.

[linawolf]

Needs to be manually preported to main