### 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
advance();
			result = parse_match();
			break;
		case GDScriptTokenizer::Token::BREAK:
			advance();
			result = parse_break();
			break;
		case GDScriptTokenizer::Token::CONTINUE:
			advance();
			result = parse_continue();
			break;
		case GDScriptTokenizer::Token::RETURN: {
			advance();
			ReturnNode *n_return = alloc_node<ReturnNode>();
			if (!is_statement_end()) {
				if (current_function && (current_function->identifier->name == GDScriptLanguage::get_singleton()->strings._init || current_function->identifier->name == GDScriptLanguage::get_singleton()->strings._static_init)) {
					push_error(R"(Constructor cannot return a value.)");
				}
				n_return->return_value = parse_expression(false);
			} else if (in_lambda && !is_statement_end_token()) {
				
				
				n_return->return_value = parse_expression(false);
			}
			complete_extents(n_return);
			result = n_return;
			current_suite->has_return = true;
			end_statement("return statement");
			break;
		}