remove all Docker Hub related feature from github

[homework36]

We have disabled the auto-build rules but somehow it still shows up "failure" on commit messages. Since we no longer use Docker Hub, I will see if we can shut down Docker Hub completely.

[homework36]

It is this thing.

Already did

• unlinked GitHub account on Docker Hub
• deleted the autobuild rule for the develop branch
• checked GitHub setting webhook and found the Docker Hub one not triggered at all

Checked everything ChatGPT suggested. We just wait for a few next PR and see if this can be gone...