### 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
type->type_chain.push_back(type_element);
	if (match(GDScriptTokenizer::Token::BRACKET_OPEN)) {
		
		type->container_type = parse_type(false); 
		if (type->container_type == nullptr) {
			push_error(R"(Expected type for collection after "[".)");
			complete_extents(type);
			type = nullptr;
		} else if (type->container_type->container_type != nullptr) {
			push_error("Nested typed collections are not supported.");
		}
		consume(GDScriptTokenizer::Token::BRACKET_CLOSE, R"(Expected closing "]" after collection type.)");
		if (type != nullptr) {
			complete_extents(type);
		}
		return type;
	}
	int chain_index = 1;
	while (match(GDScriptTokenizer::Token::PERIOD)) {
		make_completion_context(COMPLETION_TYPE_ATTRIBUTE, type, chain_index++);
		if (consume(GDScriptTokenizer::Token::IDENTIFIER, R"(Expected inner type name after ".".)")) {
			type_element = parse_identifier();
			type->type_chain.push_back(type_element);
		}
	}
	complete_extents(type);
	return type;
}
#ifdef TOOLS_ENABLED
enum DocLineState {