Missing nested table autocompletion if type defined

### How are you using the lua-language-server?

Visual Studio Code Extension (sumneko.lua)

### Which OS are you using?

Windows

### What is the issue affecting?

Completion

### Expected Behaviour


### Actual Behaviour


### Reproduction steps

1. Just paste the code into the editor, and you'll catch this autocompletion mistake

### Additional Notes

Maybe a month ago this was working. Maybe it has broken due to recent commits

### Log File

_No response_

Reproduce the reported completion problem in the Visual Studio Code extension using the example represented by the expected and actual screenshots. Trace the language server's completion handling for typed nested tables, then verify that the expected nested suggestions appear and add a regression check if the project provides a suitable completion test location.

Written by the indexing model from the issue text.