Set _choose_auto_accelerator to staticmethod (#19822)

Author: fedebotu

src/lightning/fabric/connector.py

@@ -313,7 +313,8 @@ def _check_device_config_and_set_final_flags(self, devices: Union[List[int], str
                 f" using {accelerator_name} accelerator."
             )
 
-    def _choose_auto_accelerator(self) -> str:
+    @staticmethod
+    def _choose_auto_accelerator() -> str:
         """Choose the accelerator type (str) based on availability when ``accelerator='auto'``."""
         if XLAAccelerator.is_available():
             return "tpu"

src/lightning/pytorch/trainer/connectors/accelerator_connector.py

@@ -328,7 +328,8 @@ def _check_device_config_and_set_final_flags(self, devices: Union[List[int], str
                 f" using {accelerator_name} accelerator."
             )
 
-    def _choose_auto_accelerator(self) -> str:
+    @staticmethod
+    def _choose_auto_accelerator() -> str:
         """Choose the accelerator type (str) based on availability."""
         if XLAAccelerator.is_available():
             return "tpu"