### 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
CastNode *cast = alloc_node<CastNode>();
	reset_extents(cast, p_previous_operand);
	update_extents(cast);
	cast->operand = p_previous_operand;
	cast->cast_type = parse_type();
	complete_extents(cast);
	if (cast->cast_type == nullptr) {
		push_error(R"(Expected type specifier after "as".)");
		return p_previous_operand;
	}
	return cast;
}
GDScriptParser::ExpressionNode *GDScriptParser::parse_call(ExpressionNode *p_previous_operand, bool p_can_assign) {
	CallNode *call = alloc_node<CallNode>();
	reset_extents(call, p_previous_operand);
	if (previous.type == GDScriptTokenizer::Token::SUPER) {
		
		call->is_super = true;
		push_multiline(true);
		if (match(GDScriptTokenizer::Token::PARENTHESIS_OPEN)) {
			
			if (current_function == nullptr) {
				push_error(R"(Cannot use implicit "super" call outside of a function.)");