### Godot version

4.0.2.stable

### System information

Ubuntu 22.10

### Issue description

This happens when converting a godot3 project to a godot4 project.
Godot3 source
```gdscript
extends Node2D

export(int) var integer := 2
export(Resource) var resource: Resource = null
```

Result
```gdscript
extends Node2D

@export var integer: int := 2
@export var resource: Resource: Resource = null
```

Expected result
```gdscript
extends Node2D

@export var integer := 2
@export var resource: Resource = null
```

If someone can point to where in the code this might be fixed maybe I can fix it myself, sounds like a good first issue.


### Steps to reproduce

Open the given project (or any project really) and convert it to a godot 4 project

### Minimal reproduction project

[Conversion Tool Typing Problem.zip](https://github.com/godotengine/godot/files/11185334/Conversion.Tool.Typing.Problem.zip)

String empty_space;
	int current_character = 0;
	if (line.is_empty()) {
		return empty_space;
	}
	if (line[0] == ' ') {
		while (current_character < line.size()) {
			if (line[current_character] == ' ') {
				empty_space += ' ';
				current_character++;
			} else {
				break;
			}
		}
	}
	if (line[0] == '\t') {
		while (current_character < line.size()) {
			if (line[current_character] == '\t') {
				empty_space += '\t';
				current_character++;
			} else {
				break;
			}
		}
	}
	return empty_space;
}
// Returns the object that’s executing the function in the line.
// e.g. Passing the line "var roman = kieliszek.funkcja()" to this function returns "kieliszek".
String ProjectConverter3To4::get_object_of_execution(const String &line) const {