### 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
multiline_stack.push_back(p_state);
	tokenizer.set_multiline_mode(p_state);
	if (p_state) {
		
		while (current.type == GDScriptTokenizer::Token::NEWLINE || current.type == GDScriptTokenizer::Token::INDENT || current.type == GDScriptTokenizer::Token::DEDENT) {
			current = tokenizer.scan(); 
		}
	}
}
void GDScriptParser::pop_multiline() {
	ERR_FAIL_COND_MSG(multiline_stack.size() == 0, "Parser bug: trying to pop from multiline stack without available value.");
	multiline_stack.pop_back();
	tokenizer.set_multiline_mode(multiline_stack.size() > 0 ? multiline_stack.back()->get() : false);
}
bool GDScriptParser::is_statement_end_token() const {