Variant::has_method bug

Currently if you pass a Variant to variant's has_method function it will always report false. but if you cast it to a String() before hand it works.

Example of issue:
```cpp
void Class::test(Variant var)
{
Variant method = "floor";
UtilityFunctions::print(var.has_method(method));
UtilityFunctions::print(var.has_method(method.operator String()));
}
```
The output will be:
```
false
true
```

When compiling as a module however this works as expected.

godot-cpp version: 7fb46e9