### 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
ERR_FAIL_COND_V_MSG(p_node->type != Node::FUNCTION, false, vformat(R"("%s" annotation can only be applied to functions.)", p_annotation->name));
	FunctionNode *function = static_cast<FunctionNode *>(p_node);
	if (function->rpc_config.get_type() != Variant::NIL) {
		push_error(R"(RPC annotations can only be used once per function.)", p_annotation);
		return false;
	}
	Dictionary rpc_config;
	rpc_config["rpc_mode"] = MultiplayerAPI::RPC_MODE_AUTHORITY;
	if (!p_annotation->resolved_arguments.is_empty()) {
		int last = p_annotation->resolved_arguments.size() - 1;
		if (p_annotation->resolved_arguments[last].get_type() == Variant::INT) {
			rpc_config["channel"] = p_annotation->resolved_arguments[last].operator int();
			last -= 1;
		}
		if (last > 3) {
			push_error(R"(Invalid RPC arguments. At most 4 arguments are allowed, where only the last argument can be an integer to specify the channel.')", p_annotation);
			return false;
		}
		unsigned char locality_args = 0;
		unsigned char permission_args = 0;
		unsigned char transfer_mode_args = 0;
		for (int i = last; i >= 0; i--) {
			String arg = p_annotation->resolved_arguments[i].operator String();
			if (arg == "call_local") {
				locality_args++;
				rpc_config["call_local"] = true;
			} else if (arg == "call_remote") {
				locality_args++;
				rpc_config["call_local"] = false;
			} else if (arg == "any_peer") {