### 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
parse_class_name();
				}
				break;
			case GDScriptTokenizer::Token::EXTENDS:
				advance();
				if (head->extends_used) {
					push_error(R"("extends" can only be used once.)");
				} else {
					parse_extends();
					end_statement("superclass");
				}
				break;
			case GDScriptTokenizer::Token::LITERAL:
				if (current.literal.get_type() == Variant::STRING) {
					
					advance();
					if (!match(GDScriptTokenizer::Token::NEWLINE)) {
						push_error("Expected newline after comment string.");
					}
					break;
				}
				[[fallthrough]];
			default:
				
				can_have_class_or_extends = false;
				break;
		}
		if (panic_mode) {
			synchronize();
		}