### 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
EnumNode *enum_node = alloc_node<EnumNode>();
	bool named = false;
	if (check(GDScriptTokenizer::Token::IDENTIFIER)) {
		advance();
		enum_node->identifier = parse_identifier();
		named = true;
	}
	push_multiline(true);
	consume(GDScriptTokenizer::Token::BRACE_OPEN, vformat(R"(Expected "{" after %s.)", named ? "enum name" : R"("enum")"));
	HashMap<StringName, int> elements;
#ifdef DEBUG_ENABLED
	List<MethodInfo> gdscript_funcs;
	GDScriptLanguage::get_singleton()->get_public_functions(&gdscript_funcs);
#endif
	do {
		if (check(GDScriptTokenizer::Token::BRACE_CLOSE)) {
			break; 
		}
		if (consume(GDScriptTokenizer::Token::IDENTIFIER, R"(Expected identifier for enum key.)")) {
			EnumNode::Value item;
			GDScriptParser::IdentifierNode *identifier = parse_identifier();
#ifdef DEBUG_ENABLED
			if (!named) { 
				for (MethodInfo &info : gdscript_funcs) {