### 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 could_continue = can_continue;
	
	can_break = true;
	can_continue = true;
	n_while->loop = parse_suite(R"("while" block)");
	n_while->loop->is_loop = true;
	complete_extents(n_while);
	
	can_break = could_break;
	can_continue = could_continue;
	return n_while;
}
GDScriptParser::ExpressionNode *GDScriptParser::parse_precedence(Precedence p_precedence, bool p_can_assign, bool p_stop_on_assign) {
	
	
	switch (current.type) {
		case GDScriptTokenizer::Token::PARENTHESIS_OPEN:
		case GDScriptTokenizer::Token::BRACE_OPEN:
		case GDScriptTokenizer::Token::BRACKET_OPEN:
			push_multiline(true);
			break;
		default:
			break; 
	}
	
	make_completion_context(COMPLETION_IDENTIFIER, nullptr);
	GDScriptTokenizer::Token token = current;
	GDScriptTokenizer::Token::Type token_type = token.type;
	if (token.is_identifier()) {