Remove [backingServiceSelector](https://github.com/redhat-developer/service-binding-operator/blob/master/pkg/apis/apps/v1alpha1/servicebindingrequest_types.go#L33) in favour of [backingServiceSelectors](https://github.com/redhat-developer/service-binding-operator/blob/master/pkg/apis/apps/v1alpha1/servicebindingrequest_types.go#L39)
Remove backingServiceSelector in favour of backingServiceSelectors