### 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
} else {
			member->doc_description = get_doc_comment(doc_comment_line);
		}
	}
#endif 
	if (member->identifier != nullptr) {
		if (!((String)member->identifier->name).is_empty()) { 
#ifdef DEBUG_ENABLED
			List<MethodInfo> gdscript_funcs;
			GDScriptLanguage::get_singleton()->get_public_functions(&gdscript_funcs);
			for (MethodInfo &info : gdscript_funcs) {
				if (info.name == member->identifier->name) {
					push_warning(member->identifier, GDScriptWarning::SHADOWED_GLOBAL_IDENTIFIER, p_member_kind, member->identifier->name, "built-in function");
				}
			}
			if (Variant::has_utility_function(member->identifier->name)) {
				push_warning(member->identifier, GDScriptWarning::SHADOWED_GLOBAL_IDENTIFIER, p_member_kind, member->identifier->name, "built-in function");
			}
#endif
			if (current_class->members_indices.has(member->identifier->name)) {
				push_error(vformat(R"(%s "%s" has the same name as a previously declared %s.)", p_member_kind.capitalize(), member->identifier->name, current_class->get_member(member->identifier->name).get_type_name()), member->identifier);
			} else {
				current_class->add_member(member);
			}
		} else {
			current_class->add_member(member);
		}
	}
}
void GDScriptParser::parse_class_body(bool p_is_multiline) {