self keyword not correctly specified / highlighted

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

NeoVim

### Which OS are you using?

Linux

### What is the issue affecting?

Other

### Expected Behaviour

The `self` word should be highlighted as a keyword and not a variable.

### Actual Behaviour

The `self` keyword seems to be recognized as a variable and not a keyword. The `self` keyword is not correctly highlighted. It seems highlighted as a variable and not as a keyword.

### Reproduction steps

Use `neovim` with `lua_ls` and open a `lua` file and a theme with the `self` keyword. The `self` keyword is not correctly highlighted.

### Additional Notes

I first noticed the problem in neovim with the `everforest` theme. I even opened an [issue](https://github.com/sainnhe/everforest/issues/155). More context can be found in the author's detailed answer.

### Log File

_No response_

Start by reproducing the report in Neovim with lua_ls on a Lua file, using a theme that highlights the self keyword, and review the linked Everforest issue for context. Done means self is classified and displayed as a keyword rather than a variable in the reported setup.

Written by the indexing model from the issue text.