### 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)

if (p_builtin) {
		return p_str.replace("\"", "\\\"");
	} else {
		return p_str;
	}
}
void ProjectConverter3To4::rename_gdscript_keywords(Vector<SourceLine> &source_lines, const RegExContainer &reg_container, bool builtin) {
	static String error_message = "The master and mastersync rpc behavior is not officially supported anymore. Try using another keyword or making custom logic using get_multiplayer().get_remote_sender_id()\n";
	for (SourceLine &source_line : source_lines) {
		if (source_line.is_comment) {
			continue;
		}
		String &line = source_line.line;
		if (uint64_t(line.length()) <= maximum_line_length) {
			if (line.contains("export")) {
				line = reg_container.keyword_gdscript_export_single.sub(line, "@export", true);
			}
			if (line.contains("export")) {
				line = reg_container.keyword_gdscript_export_mutli.sub(line, "$1@export", true);
			}
			if (line.contains("onready")) {