Fix incorrect getFinalizer() reference in setPollFDNotifiers()

Author: C0rn3j

usb1/__init__.py

@@ -2603,7 +2603,7 @@ def setPollFDNotifiers(
             # race-condition) it is not a big deal, as __finalizePollFDNotifiers
             # will do the right thing even if called multiple times in a row.
             self.__has_pollfd_finalizer = True
-            self.getFinalizer(
+            self._getFinalizer(
                 self,
                 self.__finalizePollFDNotifiers, # Note: staticmethod
                 context_p=self.__context_p,