### 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
	bool is_annotation = false;
	switch (current.type) {
		case GDScriptTokenizer::Token::PASS:
			advance();
			result = alloc_node<PassNode>();
			complete_extents(result);
			end_statement(R"("pass")");
			break;
		case GDScriptTokenizer::Token::VAR:
			advance();
			result = parse_variable(false, false);
			break;
		case GDScriptTokenizer::Token::CONST:
			advance();
			result = parse_constant(false);
			break;
		case GDScriptTokenizer::Token::IF:
			advance();
			result = parse_if();
			break;
		case GDScriptTokenizer::Token::FOR:
			advance();
			result = parse_for();
			break;
		case GDScriptTokenizer::Token::WHILE:
			advance();
			result = parse_while();
			break;
		case GDScriptTokenizer::Token::MATCH: