fix test (hopefully)

Author: rbri

src/test/java/org/htmlunit/WebClient2Test.java

@@ -418,8 +418,9 @@ public void localFile() throws Exception {
     @Alerts("titel - simple.html")
     public void localFileFile() throws Exception {
         final URL url = getClass().getClassLoader().getResource("simple.html");
-        String file = url.getFile();
+        String file = URLDecoder.decode(url.getFile(), StandardCharsets.UTF_8);
         if (file.startsWith("/") && file.contains(":")) {
+            // we have to remove the trailing slash to test the c:\.... case.
             file = file.substring(1);
         }