bug#62407: 30.0.50; The command to run elixir-ls on Windows is `language_server.bat`

[牟 桐]

> What is the value of shell-file-name on that Windows
> system?

It's `cmdproxy.exe` on Windows, after I changed it to `powershell.exe`
and `cmd.exe`, the eglot's guess stays the same. I guess that is because
eglot had hardcoded the result here:

https://github.com/emacs-mirror/emacs/blob/4566a0c6b825a18e6c065da0543b8b942b7db8df/lisp/progmodes/eglot.el#L224-L225

``` emacs-lisp-mode
((elixir-mode elixir-ts-mode heex-ts-mode)
 . ("language_server.sh"))
```