chore(ios): lower deployment target to iOS 11.0

Author: fadi-george

com.onesignal.unity.ios/Editor/BuildPostProcessor.cs

@@ -221,9 +221,9 @@ private void AddNotificationServiceExtension()
 
             ExtensionAddSourceFiles(extensionGuid);
 
-            // Makes it so that the extension target is Universal (not just iPhone) and has an iOS 10 deployment target
+            // Makes it so that the extension target is Universal (not just iPhone)
             _project.SetBuildProperty(extensionGuid, "TARGETED_DEVICE_FAMILY", "1,2");
-            _project.SetBuildProperty(extensionGuid, "IPHONEOS_DEPLOYMENT_TARGET", "13.0");
+            _project.SetBuildProperty(extensionGuid, "IPHONEOS_DEPLOYMENT_TARGET", "11.0");
             _project.SetBuildProperty(extensionGuid, "SWIFT_VERSION", "5.0");
             _project.SetBuildProperty(
                 extensionGuid,