### 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
return kind == GDScriptParser::DataType::BUILTIN && _variant_type_to_typed_array_element_type(builtin_type) != Variant::NIL;
}
GDScriptParser::DataType GDScriptParser::DataType::get_typed_container_type() const {
	GDScriptParser::DataType type;
	type.kind = GDScriptParser::DataType::BUILTIN;
	type.builtin_type = _variant_type_to_typed_array_element_type(builtin_type);
	return type;
}
void GDScriptParser::complete_extents(Node *p_node) {
	while (!nodes_in_progress.is_empty() && nodes_in_progress.back()->get() != p_node) {
		ERR_PRINT("Parser bug: Mismatch in extents tracking stack.");
		nodes_in_progress.pop_back();
	}
	if (nodes_in_progress.is_empty()) {
		ERR_PRINT("Parser bug: Extents tracking stack is empty.");
	} else {
		nodes_in_progress.pop_back();
	}
}
void GDScriptParser::update_extents(Node *p_node) {