Libraries: Use default constructors/destructors in LibHTTP

https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#cother-other-default-operation-rules

"The compiler is more likely to get the default semantics right and
you cannot implement these functions better than the compiler."

Userland/Libraries/LibHTTP/HttpRequest.cpp

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2022, the SerenityOS developers.
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -11,14 +12,6 @@
 
 namespace HTTP {
 
-HttpRequest::HttpRequest()
-{
-}
-
-HttpRequest::~HttpRequest()
-{
-}
-
 String HttpRequest::method_name() const
 {
     switch (m_method) {