Setting headers to null to remove them is wrong in the reverse proxy handler

Author: shs96c

java/server/src/org/openqa/selenium/grid/web/ReverseProxyHandler.java

@@ -75,8 +75,8 @@ public HttpResponse execute(HttpRequest req) throws UncheckedIOException {
     HttpResponse resp = upstream.execute(toUpstream);
 
     // clear response defaults.
-    resp.setHeader("Date",null);
-    resp.setHeader("Server",null);
+    resp.removeHeader("Date");
+    resp.removeHeader("Server");
 
     IGNORED_REQ_HEADERS.forEach(resp::removeHeader);