Catalog source poll is not required if the image refers to a digest

[ashishth09]

We can add an additional check at https://github.com/operator-framework/api/blob/master/pkg/operators/v1alpha1/catalogsource_types.go#L287 to see if image has @sha as I believe the polling to see the update is required only there is scope of image getting updated but an image referencing digest and not tag will not receive new updates via push.