### 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
GDScriptTokenizer::Token::Type invalid = previous.type;
	switch (invalid) {
		case GDScriptTokenizer::Token::QUESTION_MARK:
			push_error(R"(Unexpected "?" in source. If you want a ternary operator, use "truthy_value if true_condition else falsy_value".)");
			break;
		default:
			return nullptr; 
	}
	
	return p_previous_operand;
}
GDScriptParser::TypeNode *GDScriptParser::parse_type(bool p_allow_void) {
	TypeNode *type = alloc_node<TypeNode>();
	make_completion_context(p_allow_void ? COMPLETION_TYPE_NAME_OR_VOID : COMPLETION_TYPE_NAME, type);
	if (!match(GDScriptTokenizer::Token::IDENTIFIER)) {
		if (match(GDScriptTokenizer::Token::VOID)) {
			if (p_allow_void) {
				complete_extents(type);
				TypeNode *void_type = type;
				return void_type;
			} else {
				push_error(R"("void" is only allowed for a function return type.)");
			}
		}
		
		complete_extents(type);
		return nullptr;
	}
	IdentifierNode *type_element = parse_identifier();