### 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
push_warning(nd, GDScriptWarning::EMPTY_FILE);
	}
#endif
	push_multiline(false); 
	parse_program();
	pop_multiline();
#ifdef DEBUG_ENABLED
	if (multiline_stack.size() > 0) {
		ERR_PRINT("Parser bug: Imbalanced multiline stack.");
	}
#endif
	if (errors.is_empty()) {
		return OK;
	} else {
		return ERR_PARSE_ERROR;
	}
}
GDScriptTokenizer::Token GDScriptParser::advance() {
	lambda_ended = false; 
	if (current.type == GDScriptTokenizer::Token::TK_EOF) {
		ERR_FAIL_COND_V_MSG(current.type == GDScriptTokenizer::Token::TK_EOF, current, "GDScript parser bug: Trying to advance past the end of stream.");
	}
	if (for_completion && !completion_call_stack.is_empty()) {
		if (completion_call.call == nullptr && tokenizer.is_past_cursor()) {
			completion_call = completion_call_stack.back()->get();
			passed_cursor = true;
		}
	}
	previous = current;
	current = tokenizer.scan();