### Godot version

4.0 stable

### System information

Fedora, RX 590

### Issue description

I made a dictionary, and instead of using `:` to separate between key and value, i accidentally used `=`.
The error message was not clear at all `Parse Error: Expected identifier or string as LUA-style dictionary key.` 

I don't think assuming that people know how dictionaries are made in LUA is reasonable. And if this is not about LUA the programming language, i don't even know what this is about :D

I think this error should be replaced with something of the sort "Please use `:` as separator instead of `=` in your dictionary"

### Steps to reproduce

Paste this code in a script:

```

var dict = {
	1 = "lala"
}
```

Observe the error message
![image](https://user-images.githubusercontent.com/7917475/224549538-38ea25aa-ba75-431e-868b-0733a53b90ad.png)


### Minimal reproduction project

see above
head = alloc_node<ClassNode>();
	head->fqcn = script_path;
	current_class = head;
	bool can_have_class_or_extends = true;
	while (!check(GDScriptTokenizer::Token::TK_EOF)) {
		if (match(GDScriptTokenizer::Token::ANNOTATION)) {
			AnnotationNode *annotation = parse_annotation(AnnotationInfo::SCRIPT | AnnotationInfo::STANDALONE | AnnotationInfo::CLASS_LEVEL);
			if (annotation != nullptr) {
				if (annotation->applies_to(AnnotationInfo::SCRIPT)) {
					
					if (annotation->name == SNAME("@icon")) {
						annotation->apply(this, head);