qml: rm QEConfig.serverString. Network.server is sufficient

If there is no network object, it's ok not to be able to customise it.

electrum/gui/qml/components/ServerConfigDialog.qml

@@ -42,7 +42,6 @@ ElDialog {
             icon.source: '../../icons/confirmed.png'
             onClicked: {
                 Config.autoConnect = serverconfig.auto_connect
-                Config.serverString = serverconfig.address
                 Network.server = serverconfig.address
                 rootItem.close()
             }

electrum/gui/qml/components/ServerConnectWizard.qml

@@ -24,7 +24,6 @@ Wizard {
         Config.autoConnect = wizard_data['autoconnect']
         if (!wizard_data['autoconnect']) {
             Network.server = wizard_data['server']
-            Config.serverString = wizard_data['server']
         }
     }
 

electrum/gui/qml/components/controls/ServerConfig.qml

@@ -93,7 +93,7 @@ Item {
 
     Component.onCompleted: {
         root.auto_connect = Config.autoConnectDefined ? Config.autoConnect : false
-        root.address = Config.serverString ? Config.serverString : Network.server
+        root.address = Network.server
         // TODO: initial setup should not connect already, is Network.server defined?
     }
 }

electrum/gui/qml/qeconfig.py

@@ -57,16 +57,6 @@ class QEConfig(AuthMixin, QObject):
     def autoConnectDefined(self):
         return self.config.get('auto_connect') is not None
 
-    serverStringChanged = pyqtSignal()
-    @pyqtProperty('QString', notify=serverStringChanged)
-    def serverString(self):
-        return self.config.get('server')
-
-    @serverString.setter
-    def serverString(self, server):
-        self.config.set_key('server', server, True)
-        self.serverStringChanged.emit()
-
     manualServerChanged = pyqtSignal()
     @pyqtProperty(bool, notify=manualServerChanged)
     def manualServer(self):