### 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
bool class_end = false;
	bool next_is_static = false;
	while (!class_end && !is_at_end()) {
		GDScriptTokenizer::Token token = current;
		switch (token.type) {
			case GDScriptTokenizer::Token::VAR:
				parse_class_member(&GDScriptParser::parse_variable, AnnotationInfo::VARIABLE, "variable", next_is_static);
				if (next_is_static) {
					current_class->has_static_data = true;
				}
				break;
			case GDScriptTokenizer::Token::CONST:
				parse_class_member(&GDScriptParser::parse_constant, AnnotationInfo::CONSTANT, "constant");
				break;
			case GDScriptTokenizer::Token::SIGNAL:
				parse_class_member(&GDScriptParser::parse_signal, AnnotationInfo::SIGNAL, "signal");
				break;
			case GDScriptTokenizer::Token::FUNC:
				parse_class_member(&GDScriptParser::parse_function, AnnotationInfo::FUNCTION, "function", next_is_static);
				break;
			case GDScriptTokenizer::Token::CLASS:
				parse_class_member(&GDScriptParser::parse_class, AnnotationInfo::CLASS, "class");
				break;
			case GDScriptTokenizer::Token::ENUM:
				parse_class_member(&GDScriptParser::parse_enum, AnnotationInfo::NONE, "enum");
				break;
			case GDScriptTokenizer::Token::STATIC: {
				advance();
				next_is_static = true;
				if (!check(GDScriptTokenizer::Token::FUNC) && !check(GDScriptTokenizer::Token::VAR)) {