ScriptEditor::reload_scripts: Only call deferred if not main thread

[nikitalita]

Sometimes we need to wait for the scripts to be fully reloaded before doing other stuff to update the editor state, and this becomes a problem because reload_scripts always ends up calling deferred, when it's not necessary.

According to @kitbdev , who made the original change to make reload_scripts call deferred:

It doesn't need to be deferred, it just needs to be on the main thread.

[kitbdev]

Makes sense.
Tested for a bit to make sure #71016 didn't return, looks good.

#99861 also deferred the calling of this, so it was being deferred twice in some cases when it doesn't need to be.

[Repiteo]

Thanks!