### 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
if (found) {
				break;
			}
			cursor_line++;
			cursor_column = 1;
		}
		source = source.replace_first(String::chr(0xFFFF), String());
	}
	tokenizer.set_source_code(source);
	tokenizer.set_cursor_position(cursor_line, cursor_column);
	script_path = p_script_path;
	current = tokenizer.scan();
	
	
	while (current.type == GDScriptTokenizer::Token::ERROR || current.type == GDScriptTokenizer::Token::NEWLINE) {
		if (current.type == GDScriptTokenizer::Token::ERROR) {
			push_error(current.literal);
		}
		current = tokenizer.scan();
	}
#ifdef DEBUG_ENABLED
	
	if (current.type == GDScriptTokenizer::Token::TK_EOF) {
		
		Node *nd = alloc_node<PassNode>();
		nd->start_line = 1;
		nd->start_column = 0;
		nd->end_line = 1;
		nd->leftmost_column = 0;
		nd->rightmost_column = 0;