[FLINK-33626] Revert accidentally committed changes to docs

[snuyanzin]

What is the purpose of the change

This the revert of changes in docs accidentally introduced in #23751

Verifying this change

$ git submodule update --init --recursive
$ ./setup_docs.sh
$ docker pull jakejarvis/hugo-extended:latest
$ docker run -v $(pwd):/src -p 1313:1313 jakejarvis/hugo-extended:latest server --buildDrafts --buildFuture --bind 0.0.0.0

and look into docs locally

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): ( no)
• The public API, i.e., is any changed class annotated with @Public(Evolving): ( no)
• The serializers: ( no)
• The runtime per-record code paths (performance sensitive): ( no)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: ( no)
• The S3 file system connector: ( no )

Documentation

• Does this pull request introduce a new feature? ( no)
• If yes, how is the feature documented? (not applicable)

[snuyanzin]

@WencongLiu , @FangYongs could you please have a look here since you are participating in jira issue?

[flinkbot]

CI report:

• fea1315 Azure: SUCCESS

Bot commands

The @flinkbot bot supports the following commands:

• @flinkbot run azure re-run the last Azure build

[RyanSkraba]

LGTM - I checked that the website builds without the navigation bar glitches after the submodule is restored.

[XComp]

LGTM2 👍

I noticed that as well that the book submodule changed in my local checkout. I had to revert it manually. Shall we investigate further why this happened as part of FLINK-33626? Or shall we create a new Jira issue. I'd say keeping FLINK-33626 open till this is fixed should be sufficient enough. 🤔

[snuyanzin]

Thanks for taking a look
I will try to investigate more within FLINK-33626 to find the root cause