Use anonymous namespace for constants

src/device/devicedatabasebackend.cpp

@@ -38,7 +38,9 @@
 #include "core/scopedtransaction.h"
 #include "devicedatabasebackend.h"
 
-const int DeviceDatabaseBackend::kDeviceSchemaVersion = 5;
+namespace {
+constexpr int kDeviceSchemaVersion = 5;
+}
 
 DeviceDatabaseBackend::DeviceDatabaseBackend(QObject *parent)
     : QObject(parent),

src/device/devicedatabasebackend.h

@@ -56,8 +56,6 @@ class DeviceDatabaseBackend : public QObject {
   };
   using DeviceList = QList<Device>;
 
-  static const int kDeviceSchemaVersion;
-
   void Init(SharedPtr<Database> db);
   void Close();
   void ExitAsync();