[segmentation.models] Fix docstrings

src/mednet/libs/segmentation/config/models/unet.py

 # SPDX-FileCopyrightText: Copyright © 2024 Idiap Research Institute <contact@idiap.ch>
 #
 # SPDX-License-Identifier: GPL-3.0-or-later
-"""Little W-Net for image segmentation.
 
-The Little W-Net architecture contains roughly around 70k parameters and
-closely matches (or outperforms) other more complex techniques.
+"""U-Net for image segmentation.
 
-Reference: [GALDRAN-2020]_
+U-Net is a convolutional neural network that was developed for biomedical image
+segmentation at the Computer Science Department of the University of Freiburg,
+Germany.  The network is based on the fully convolutional network (FCN) and its
+architecture was modified and extended to work with fewer training images and
+to yield more precise segmentations.
+
+Reference: [RONNEBERGER-2015]_
 """
 
 from mednet.libs.segmentation.engine.adabound import AdaBound