fix remove test

Author: bparrishMines

packages/webview_flutter/webview_flutter_android/android/src/main/java/io/flutter/plugins/webviewflutter/AndroidWebkitLibrary.g.kt

@@ -155,6 +155,10 @@ class AndroidWebkitLibraryPigeonInstanceManager(
    */
   fun <T> remove(identifier: Long): T? {
     logWarningIfFinalizationListenerHasStopped()
+    val instance: Any? = getInstance(identifier)
+    if (instance is WebViewProxyApi.WebViewPlatformView) {
+      instance.destroy()
+    }
     return strongInstances.remove(identifier) as T?
   }