Update to pandera >0.19.3

[jluethi]

The current main pandera 0.20.3 leads to input errors in our feature_loader plugin.

Failed to import command at 'napari_feature_classifier.feature_loader_widget:load_features_factory': module 'pandera' has no attribute 'SchemaModel'

For the moment, I'll pin pandera to 0.19.3. If we want to update to newer pandera versions, we'll need to update to their breaking changes to become robust against them. Even if we fix this import error, I suggest we keep pandera pinned to a given version to avoid such issues.