Correct Python to Godot string conversion to avoid useless intermedia…

…ry encoding in `_load_singleton`

src/godot/classes.pyx.j2

@@ -96,7 +96,7 @@ cdef object _load_singleton(str name):
 
     cdef object cls = _load_class(name)
 {# cdef GDExtensionObjectPtr gdobj = pythonscript_gdextension.global_get_singleton(&(<StringName>cls._gd_name)._gd_data) #}
-    cdef gd_string_name_t gdname = gd_string_name_from_utf8(name.encode())
+    cdef gd_string_name_t gdname = gd_string_name_from_unchecked_pystr(name)
     cdef GDExtensionObjectPtr gdobj = pythonscript_gdextension.global_get_singleton(&gdname)
     gd_string_name_del(&gdname)
     cdef object singleton = cls._from_ptr(<size_t>gdobj)