### 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
}
			}
		}
	}
#endif 
	complete_extents(enum_node);
	end_statement("enum");
	return enum_node;
}
void GDScriptParser::parse_function_signature(FunctionNode *p_function, SuiteNode *p_body, const String &p_type) {
	if (!check(GDScriptTokenizer::Token::PARENTHESIS_CLOSE) && !is_at_end()) {
		bool default_used = false;
		do {
			if (check(GDScriptTokenizer::Token::PARENTHESIS_CLOSE)) {
				
				break;
			}
			ParameterNode *parameter = parse_parameter();
			if (parameter == nullptr) {
				break;
			}
			if (parameter->initializer != nullptr) {
				default_used = true;
			} else {
				if (default_used) {
					push_error("Cannot have mandatory parameters after optional parameters.");
					continue;
				}
			}
			if (p_function->parameters_indices.has(parameter->identifier->name)) {