### 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
decrease_indent();
			}
		}
	}
	decrease_indent();
	push_line();
}
void GDScriptParser::TreePrinter::print_while(WhileNode *p_while) {
	push_text("While ");
	print_expression(p_while->condition);
	push_line(" :");
	increase_indent();
	print_suite(p_while->loop);
	decrease_indent();
}
void GDScriptParser::TreePrinter::print_tree(const GDScriptParser &p_parser) {
	ERR_FAIL_COND_MSG(p_parser.get_tree() == nullptr, "Parse the code before printing the parse tree.");
	if (p_parser.is_tool()) {
		push_line("@tool");
	}
	if (!p_parser.get_tree()->icon_path.is_empty()) {
		push_text(R"(@icon (")");
		push_text(p_parser.get_tree()->icon_path);
		push_line("\")");
	}
	print_class(p_parser.get_tree());
	print_line(String(printed));
}
#endif