Adapt model gallery description
Model gallery
=============
-In general the models are grouped into the following categories:
+The model gallery provides a visual overview of the available models in Gammapy. In general
+the models are grouped into the following categories:
- `~gammapy.modeling.models.SpectralModel`: models to describe spectral shapes of sources
- `~gammapy.modeling.models.SpatialModel`: models to describe spatial shapes (morphologies) of sources
- `~gammapy.modeling.models.TemporalModel`: models to describe temporal flux evolution of sources, such as light and phase curves
-- `~gammapy.modeling.models.SkyModel` and `~gammapy.modeling.models.SkyDiffuseCube`: model to combine the spectral and spatial model components
-The models follow a naming scheme which contains the category as a suffix to the class
-name.
-
-The model gallery provides a visual overview of the available models in Gammapy.
+The models follow a naming scheme which contains the category as a suffix to the class name.
