PluginLib: Don't use foreach

For some reason it makes android studio angry when embedding the
plugin lib in it.

Test: runtest systemui
Change-Id: I8c7202846903a75ffcbad86cb31862098e8d939a

packages/SystemUI/plugin/src/com/android/systemui/plugins/PluginInstanceManager.java

@@ -114,7 +114,9 @@ public class PluginInstanceManager<T extends Plugin> {
 
     public void disableAll() {
         ArrayList<PluginInfo> plugins = new ArrayList<>(mPluginHandler.mPlugins);
-        plugins.forEach(this::disable);
+        for (int i = 0; i < plugins.size(); i++) {
+            disable(plugins.get(i));
+        }
     }
 
     private void disable(PluginInfo info) {