### 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
if (info.name == identifier->name) {
						push_warning(identifier, GDScriptWarning::SHADOWED_GLOBAL_IDENTIFIER, "enum member", identifier->name, "built-in function");
					}
				}
				if (Variant::has_utility_function(identifier->name)) {
					push_warning(identifier, GDScriptWarning::SHADOWED_GLOBAL_IDENTIFIER, "enum member", identifier->name, "built-in function");
				} else if (ClassDB::class_exists(identifier->name)) {
					push_warning(identifier, GDScriptWarning::SHADOWED_GLOBAL_IDENTIFIER, "enum member", identifier->name, "global class");
				}
			}
#endif
			item.identifier = identifier;
			item.parent_enum = enum_node;
			item.line = previous.start_line;
			item.leftmost_column = previous.leftmost_column;
			item.rightmost_column = previous.rightmost_column;
			if (elements.has(item.identifier->name)) {
				push_error(vformat(R"(Name "%s" was already in this enum (at line %d).)", item.identifier->name, elements[item.identifier->name]), item.identifier);
			} else if (!named) {
				if (current_class->members_indices.has(item.identifier->name)) {
					push_error(vformat(R"(Name "%s" is already used as a class %s.)", item.identifier->name, current_class->get_member(item.identifier->name).get_type_name()));
				}
			}
			elements[item.identifier->name] = item.line;
			if (match(GDScriptTokenizer::Token::EQUAL)) {
				ExpressionNode *value = parse_expression(false);
				if (value == nullptr) {
					push_error(R"(Expected expression value after "=".)");
				}
				item.custom_value = value;