Literal String as int (or float) cast causes Parser Error "Cannot cast a value of type "String" as "int"." although it works with variable String

### Tested versions

- Reproducible v4.2.1.stable.official [b09f793f5]

### System information

Godot v4.2.1.stable - Ubuntu 22.04.4 LTS 22.04 - X11 - Vulkan (Mobile) - dedicated NVIDIA GeForce GTX 860M (nvidia; 535.161.07) - Intel(R) Core(TM) i7-4710HQ CPU @ 2.50GHz (8 Threads)

### Issue description

When trying to cast a **literal string** like `"52"` into an integer (or float) using the `as` syntax, the Parser shows an Error:

> "Cannot cast a value of type "String" as "int".

(or float resp.)

This is a regression over https://github.com/godotengine/godot/issues/67494 which was fixed by https://github.com/godotengine/godot/pull/62814 and I even checked the test code suggested at the end. I also added `to_int` and the case of variable strings to demonstrate it works otherwise:

```gd
function _ready():
var a1 = "42"
assert(a1 is String)

# Expected: Parser Error "Cannot assign a value of type "String" as "int"."
#var a2 : int = "42"

# Should pass, but get "Cannot cast a value of type "String" as "int"."
var a3 : int = "42" as int
assert(a3 is int)

# BUT this works with a variable
var s3 := "42"
var b3 : int = s3 as int
assert(b3 is int)

var a4 := "42"
assert(a4 is String)

# Should pass, but get "Cannot cast a value of type "String" as "int"."
var a5 := "42" as int
assert(a5 is int)

# BUT this works with a variable
var s5 := "42"
var b5 := s5 as int
assert(b5 is int)

var a6 = int("42")
assert(a6 is int)

var a7 = "42".to_int()
assert(a7 is int)
```


### Steps to reproduce

1. Copy the demonstration code snippet above in any project script and add a node with that script
2. Let parser error show unexpected errors in red
3. You can also force parsing by running the game, but it shouldn't be needed

### Minimal reproduction project (MRP)

N/A

Start by reproducing the parser error with the provided GDScript snippet in a Godot 4.2.1 project, then trace the parser path handling `as int` and `as float` for literals versus variables. Done means literal string casts parse consistently with variable-string casts without regressing the working `int("42")` and `.to_int()` cases.

Written by the indexing model from the issue text.