### 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
ArrayNode *array = alloc_node<ArrayNode>();
	if (!check(GDScriptTokenizer::Token::BRACKET_CLOSE)) {
		do {
			if (check(GDScriptTokenizer::Token::BRACKET_CLOSE)) {
				
				break;
			}
			ExpressionNode *element = parse_expression(false);
			if (element == nullptr) {
				push_error(R"(Expected expression as array element.)");
			} else {
				array->elements.push_back(element);
			}
		} while (match(GDScriptTokenizer::Token::COMMA) && !is_at_end());
	}
	pop_multiline();
	consume(GDScriptTokenizer::Token::BRACKET_CLOSE, R"(Expected closing "]" after array elements.)");
	complete_extents(array);
	return array;
}
GDScriptParser::ExpressionNode *GDScriptParser::parse_dictionary(ExpressionNode *p_previous_operand, bool p_can_assign) {