### 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
ClassNode *n_class = alloc_node<ClassNode>();
	ClassNode *previous_class = current_class;
	current_class = n_class;
	n_class->outer = previous_class;
	if (consume(GDScriptTokenizer::Token::IDENTIFIER, R"(Expected identifier for the class name after "class".)")) {
		n_class->identifier = parse_identifier();
		if (n_class->outer) {
			String fqcn = n_class->outer->fqcn;
			if (fqcn.is_empty()) {
				fqcn = script_path;
			}
			n_class->fqcn = fqcn + "::" + n_class->identifier->name;
		} else {
			n_class->fqcn = n_class->identifier->name;
		}
	}
	if (match(GDScriptTokenizer::Token::EXTENDS)) {
		parse_extends();
	}
	consume(GDScriptTokenizer::Token::COLON, R"(Expected ":" after class declaration.)");
	bool multiline = match(GDScriptTokenizer::Token::NEWLINE);
	if (multiline && !consume(GDScriptTokenizer::Token::INDENT, R"(Expected indented block after class declaration.)")) {
		current_class = previous_class;
		complete_extents(n_class);
		return n_class;
	}
	if (match(GDScriptTokenizer::Token::EXTENDS)) {
		if (n_class->extends_used) {