style: remove pointless name-mangled attrs

the fact that removing them didn't break anything shows that they
were completely unneccessary - there is no inheritance tree
using the same names

src/aare/gui/threads/camera_thread.py

@@ -43,7 +43,7 @@ class SampleCameraThread(QThread):
         self._camera_available = False
         self._last_camera_error: str | None = None
 
-    def __set_camera_available(self, available: bool, error: str | None = None) -> None:
+    def _set_camera_available(self, available: bool, error: str | None = None) -> None:
         if available != self._camera_available:
             self._camera_available = available
             self.camera_availability_changed.emit(available)