Question mark optional syntax not supported in fun() declarations

### 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?

Type Checking

### Expected Behaviour

Optional value to actually be optional

### Actual Behaviour

It's not optional.
This code block should show as Human? and throw warnings for not checking nil. If I manually annotate with `---@param man Human?` this works as expected.

The class in question:
```lua
---@class Command
---@field info string What the command does.
---@field usage string? How to use the command.
---@field alias string[]? Aliases of the command.
---@field canCall (fun(player: Player): boolean)? Function which checks whether a player can call this command.
---@field call fun(player: Player, human: Human?, args: string[]) Calls the command.
---@field autoComplete fun(args: string[])? Function which manipulates arguments when pressing tab in the terminal.
---@field cooldownTime number? How many seconds a player has to wait before using the command again.
```

I have also tried with human?: Human and human?: Human? but neither way works.

### Reproduction steps

1. Create class with a field with a short form function declaration with an optional value parameter
2. Attempt to create object of class with that field,
3. Parameter correctly types, except as not optional.

### Additional Notes

_No response_

### Log File

_No response_

Start by reproducing the class-field example in the Visual Studio Code extension, focusing on the short-form function declaration with a nullable Human parameter. Compare it with the manually annotated `---@param man Human?` case; done means the parameter is inferred as optional and nil-check warnings appear as described.

Written by the indexing model from the issue text.