always hide pgp snackbar after decrypting a message. fixes #1075

src/main/java/eu/siacs/conversations/ui/ConversationFragment.java

@@ -764,6 +764,7 @@ public class ConversationFragment extends Fragment implements EditMessage.Keyboa
 					} catch (final NoSuchElementException ignored) {
 
 					}
+					askForPassphraseIntent = null;
 					activity.xmppConnectionService.updateMessage(message);
 				}