### 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 (current.get_identifier() == "get" || current.get_identifier() == "set") {
						return parse_property(variable, false);
					}
				}
			}
			
			variable->datatype_specifier = parse_type();
		}
	}
	if (match(GDScriptTokenizer::Token::EQUAL)) {
		
		variable->initializer = parse_expression(false);
		if (variable->initializer == nullptr) {
			push_error(R"(Expected expression for variable initial value after "=".)");
		}
		variable->assignments++;
	}
	if (p_allow_property && match(GDScriptTokenizer::Token::COLON)) {
		if (match(GDScriptTokenizer::Token::NEWLINE)) {
			return parse_property(variable, true);
		} else {
			return parse_property(variable, false);
		}
	}
	complete_extents(variable);
	end_statement("variable declaration");
	return variable;
}
GDScriptParser::VariableNode *GDScriptParser::parse_property(VariableNode *p_variable, bool p_need_indent) {