docs: ko: fix: update `_toctree.yml`
# What does this PR do?

Resolve conflicts raised by a recent `_toctree.yml` change (#23049)

* Edited some titles to match the new coherent style.
* Moved sections to match the English table of contents.
* As all of the two removed files were yet to be translated, no work was needed.
Closing in favor of #23112 <|||||>Checking if same conflicts emerge with these changes as colleague's branch is experiencing.<|||||>_The documentation is not available anymore as the PR was closed or merged._<|||||>Closing again in favor of #23112 (Checks are passing)<|||||>The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_23113). All of your documentation changes will be reflected on that endpoint.