[hotfix][rest][tests] Cleanup

This reverts commit 69de4b66b27f4b83e3b5fff59dfc793209c72640.
diff --git a/flink-runtime-web/src/test/java/org/apache/flink/runtime/webmonitor/utils/WebFrontendBootstrapTest.java b/flink-runtime-web/src/test/java/org/apache/flink/runtime/webmonitor/utils/WebFrontendBootstrapTest.java
index 42c2491..5deba65 100644
--- a/flink-runtime-web/src/test/java/org/apache/flink/runtime/webmonitor/utils/WebFrontendBootstrapTest.java
+++ b/flink-runtime-web/src/test/java/org/apache/flink/runtime/webmonitor/utils/WebFrontendBootstrapTest.java
@@ -61,8 +61,9 @@
         configuration.setString(
                 Prio0InboundChannelHandlerFactory.REDIRECT_FROM_URL, "/nonExisting");
         configuration.setString(Prio0InboundChannelHandlerFactory.REDIRECT_TO_URL, "/index.html");
-        Router router =
-                new Router().addGet("/:*", new HistoryServerStaticFileServerHandler(webDir));
+        Router<?> router =
+                new Router<>()
+                        .addGet("/:*", new HistoryServerStaticFileServerHandler(webDir.toFile()));
         WebFrontendBootstrap webUI =
                 new WebFrontendBootstrap(
                         router,