Fix idedata test mock to use Path instead of str

The test set mock_image.path to str, but FlashImage.path is a Path.
This masked a pre-existing bug where Path.endswith() doesn't exist.
Fix the mock to match the real type so as_posix() works correctly.

tests/dashboard/test_web_server.py

@@ -422,7 +422,7 @@ async def test_download_binary_handler_idedata_fallback(
 
     # Mock idedata response
     mock_image = Mock()
-    mock_image.path = str(bootloader_file)
+    mock_image.path = bootloader_file
     mock_idedata_instance = Mock()
     mock_idedata_instance.extra_flash_images = [mock_image]
     mock_idedata.return_value = mock_idedata_instance