Add View store mock to retrylayer test genStore helper

The View store was added to the store interface but the genStore()
helper in retrylayer_test.go was not updated, causing TestRetry to panic.
Also removes the duplicate Recap mock registration.

server/channels/store/retrylayer/retrylayer_test.go

@@ -72,7 +72,7 @@ func genStore() *mocks.Store {
 	mock.On("ReadReceipt").Return(&mocks.ReadReceiptStore{})
 	mock.On("Recap").Return(&mocks.RecapStore{})
 	mock.On("TemporaryPost").Return(&mocks.TemporaryPostStore{})
-	mock.On("Recap").Return(&mocks.RecapStore{})
+	mock.On("View").Return(&mocks.ViewStore{})
 	return mock
 }