Removed panelElemName - appears to not be used anywhere (#8313)

public/app/core/directives/plugin_component.ts

@@ -61,7 +61,6 @@ function pluginDirectiveLoader($compile, datasourceSrv, $rootScope, $q, $http, $
       attrs: {dashboard: "ctrl.dashboard", panel: "panel", row: "ctrl.row"},
     };
 
-    var panelElemName = 'panel-' + scope.panel.type;
     let panelInfo = config.panels[scope.panel.type];
     var panelCtrlPromise = Promise.resolve(UnknownPanelCtrl);
     if (panelInfo) {