HTTP creds: Fix translation of the password input dialog

tr() needs Q_OBJECT

src/libsync/creds/httpcredentials.h

@@ -75,6 +75,7 @@ private:
 };
 
 class OWNCLOUDSYNC_EXPORT HttpCredentialsGui : public HttpCredentials {
+    Q_OBJECT
 public:
     explicit HttpCredentialsGui() : HttpCredentials() {}
     HttpCredentialsGui(const QString& user, const QString& password, const QString& certificatePath, const QString& certificatePasswd) : HttpCredentials(user, password, certificatePath, certificatePasswd) {}