Editor documentation is not updating

### Tested versions
master

### System information

win10 21H2,Vulkan API 1.2.0

### Issue description

comment out: **//Engine::get_singleton()->add_singleton(Engine::Singleton("WorkerThreadPool", worker_thread_pool));**
start editor, in docs ZdSpace singleton still existed.
Trying to comment out other singleton is the same.

but, I del dir "editor_data/cache" and restart editor, document will be updated.

### Steps to reproduce

look at up

### Minimal reproduction project (MRP)

use commit 1d3c4e192c

Start by reproducing the report at commit 1d3c4e192c: comment out the shown WorkerThreadPool singleton registration, launch the editor, and inspect the generated documentation. Compare behavior before and after deleting editor_data/cache. Done means editor documentation reflects singleton changes after restart without requiring manual cache deletion.

Written by the indexing model from the issue text.