### 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 (!can_continue) {
		push_error(R"(Cannot use "continue" outside of a loop.)");
	}
	current_suite->has_continue = true;
	ContinueNode *cont = alloc_node<ContinueNode>();
	complete_extents(cont);
	end_statement(R"("continue")");
	return cont;
}
GDScriptParser::ForNode *GDScriptParser::parse_for() {
	ForNode *n_for = alloc_node<ForNode>();
	if (consume(GDScriptTokenizer::Token::IDENTIFIER, R"(Expected loop variable name after "for".)")) {
		n_for->variable = parse_identifier();
	}
	consume(GDScriptTokenizer::Token::IN, R"(Expected "in" after "for" variable name.)");
	n_for->list = parse_expression(false);
	if (!n_for->list) {
		push_error(R"(Expected iterable after "in".)");
	}
	consume(GDScriptTokenizer::Token::COLON, R"(Expected ":" after "for" condition.)");
	
	bool could_break = can_break;
	bool could_continue = can_continue;
	
	can_break = true;