### 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 (p_call->is_super) {
		push_text("super");
		if (p_call->callee != nullptr) {
			push_text(".");
			print_expression(p_call->callee);
		}
	} else {
		print_expression(p_call->callee);
	}
	push_text("( ");
	for (int i = 0; i < p_call->arguments.size(); i++) {
		if (i > 0) {
			push_text(" , ");
		}
		print_expression(p_call->arguments[i]);
	}
	push_text(" )");
}
void GDScriptParser::TreePrinter::print_cast(CastNode *p_cast) {
	print_expression(p_cast->operand);
	push_text(" AS ");
	print_type(p_cast->cast_type);
}
void GDScriptParser::TreePrinter::print_class(ClassNode *p_class) {