cleanup: Mark unused arguments as unused

This will stop eslint from warning about them, while keeping their
self-documenting benefit.

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/627

js/ui/status/keyboard.js

@@ -657,7 +657,7 @@ var InputSourceManager = class {
         return false;
     }
 
-    _ibusSetContentType(im, purpose, hints) {
+    _ibusSetContentType(im, purpose, _hints) {
         if (purpose == IBus.InputPurpose.PASSWORD) {
             if (Object.keys(this._inputSources).length == Object.keys(this._ibusSources).length)
                 return;

js/ui/status/network.js

@@ -149,7 +149,7 @@ var NMConnectionItem = class {
         this._sync();
     }
 
-    _connectionStateChanged(ac, newstate, reason) {
+    _connectionStateChanged(_ac, _newstate, _reason) {
         this._sync();
     }
 
@@ -222,7 +222,7 @@ var NMConnectionSection = class NMConnectionSection {
         return _("Connect");
     }
 
-    _connectionValid(connection) {
+    _connectionValid(_connection) {
         return true;
     }
 
@@ -377,7 +377,7 @@ var NMConnectionDevice = class NMConnectionDevice extends NMConnectionSection {
         this._client.activate_connection_async(connection, this._device, null, null, null);
     }
 
-    deactivateConnection(activeConnection) {
+    deactivateConnection(_activeConnection) {
         this._device.disconnect(null);
     }
 
@@ -1708,7 +1708,7 @@ var NMApplet = class extends PanelMenu.SystemIndicator {
         this._source.notify(this._notification);
     }
 
-    _onActivationFailed(device, reason) {
+    _onActivationFailed(_device, _reason) {
         // XXX: nm-applet has no special text depending on reason
         // but I'm not sure of this generic message
         this._notify('network-error-symbolic',