We have DISABLED_REPO_UNITS in the document, but it is a fake config option

### Description

As the title, I can't find any process to deal with `DISABLED_REPO_UNITS`

### Gitea Version

latest

### Can you reproduce the bug on the Gitea demo site?

No

### Log Gist

_No response_

### Screenshots

_No response_

### Git Version

_No response_

### Operating System

_No response_

### How are you running Gitea?

build

### Database

None