Doc: Document feature store objects deletion from feast

Is your feature request related to a problem? Please describe. Feast currently supports the objects deletion from registry, but its not documented yet. The object deletion is done via : feast.apply(objects_to_delete=[feature_view1])

Describe the solution you'd like

1. Document the object deletion using a jupyter notebook that:

• Creates feature store objects.
• Read the feature store objects.
• Deletes the objects.
• Validate the deleted objects are not available.

2. [Optional] Write an unit test.