Minor: use constants in internal::

UpdatePTUDevCtrl/process/check_and_fetch_customer_repository_command.h

@@ -10,6 +10,7 @@ public:
                                                     int nextCommandIndex,
                                                     int start_timeout = 100000,
                                                     int finish_timeout = 100000);
+    QString m_commandResult{};
 public slots:
     virtual void readyReadStandardOutput() override;
     virtual void finished(int exitCode, QProcess::ExitStatus exitStatus) override;