### 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
}
					}
					break;
				case DictionaryNode::PYTHON_DICT:
					if (!match(GDScriptTokenizer::Token::COLON)) {
						if (match(GDScriptTokenizer::Token::EQUAL)) {
							push_error(R"(Expected ":" after dictionary key. Mixing dictionary styles is not allowed.)");
							advance(); 
						} else {
							push_error(R"(Expected ":" after dictionary key.)");
						}
					}
					break;
			}
			
			ExpressionNode *value = parse_expression(false);
			if (value == nullptr) {
				push_error(R"(Expected expression as dictionary value.)");
			}
			if (key != nullptr && value != nullptr) {
				dictionary->elements.push_back({ key, value });
			}
		} while (match(GDScriptTokenizer::Token::COMMA) && !is_at_end());
	}
	pop_multiline();
	consume(GDScriptTokenizer::Token::BRACE_CLOSE, R"(Expected closing "}" after dictionary elements.)");
	complete_extents(dictionary);
	return dictionary;
}
GDScriptParser::ExpressionNode *GDScriptParser::parse_grouping(ExpressionNode *p_previous_operand, bool p_can_assign) {