Fix another sonar complaint

Author: maxnoe

src/ctapipe/calib/camera/__init__.py

@@ -6,7 +6,7 @@
 from .calibrator import CameraCalibrator  # noqa: F401
 from .gainselection import GainSelector  # noqa: F401
 
-__all__ = [
-    # "CameraCalibrator",
-    # "GainSelector",
-]
+# CameraCalibrator and GainSelector not added to __all__ here to avoid
+# docs build error as it would result in the class being exposed at 3 levels
+# which is not supported by sphinx
+__all__ = []