Minor cleanup

- Add pending intent immutable flags to satisfy lint warnings
- Change AddDuplicateMangaDialog arg to a function instead to avoid leaking controller-specific logic into it
- Require WebView 99+

app/src/main/java/eu/kanade/tachiyomi/App.kt

@@ -99,7 +99,7 @@ open class App : Application(), DefaultLifecycleObserver, ImageLoaderFactory {
                             this@App,
                             0,
                             Intent(ACTION_DISABLE_INCOGNITO_MODE),
-                            PendingIntent.FLAG_ONE_SHOT,
+                            PendingIntent.FLAG_ONE_SHOT or PendingIntent.FLAG_IMMUTABLE,
                         )
                         setContentIntent(pendingIntent)
                     }