### 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
print_identifier(p_parameter->identifier);
	if (p_parameter->datatype_specifier != nullptr) {
		push_text(" : ");
		print_type(p_parameter->datatype_specifier);
	}
	if (p_parameter->initializer != nullptr) {
		push_text(" = ");
		print_expression(p_parameter->initializer);
	}
}
void GDScriptParser::TreePrinter::print_preload(PreloadNode *p_preload) {
	push_text(R"(Preload ( ")");
	push_text(p_preload->resolved_path);
	push_text(R"(" )");
}
void GDScriptParser::TreePrinter::print_return(ReturnNode *p_return) {
	push_text("Return");
	if (p_return->return_value != nullptr) {
		push_text(" ");
		print_expression(p_return->return_value);
	}
	push_line();
}
void GDScriptParser::TreePrinter::print_self(SelfNode *p_self) {