### 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
if (!consume(GDScriptTokenizer::Token::IDENTIFIER, R"(Expected parameter name.)")) {
		return nullptr;
	}
	ParameterNode *parameter = alloc_node<ParameterNode>();
	parameter->identifier = parse_identifier();
	if (match(GDScriptTokenizer::Token::COLON)) {
		if (check((GDScriptTokenizer::Token::EQUAL))) {
			
			parameter->infer_datatype = true;
		} else {
			
			make_completion_context(COMPLETION_TYPE_NAME, parameter);
			parameter->datatype_specifier = parse_type();
		}
	}
	if (match(GDScriptTokenizer::Token::EQUAL)) {
		
		parameter->initializer = parse_expression(false);
	}
	complete_extents(parameter);
	return parameter;
}
GDScriptParser::SignalNode *GDScriptParser::parse_signal(bool p_is_static) {
	SignalNode *signal = alloc_node<SignalNode>();
	if (!consume(GDScriptTokenizer::Token::IDENTIFIER, R"(Expected signal name after "signal".)")) {
		complete_extents(signal);
		return nullptr;
	}
	signal->identifier = parse_identifier();
	if (check(GDScriptTokenizer::Token::PARENTHESIS_OPEN)) {