Libraries: Use default constructors/destructors in LibGUI

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/LibGUI/TextBox.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
  */
@@ -19,10 +20,6 @@ TextBox::TextBox()
     set_fixed_height(22);
 }
 
-TextBox::~TextBox()
-{
-}
-
 void TextBox::keydown_event(GUI::KeyEvent& event)
 {
     TextEditor::keydown_event(event);
@@ -87,10 +84,6 @@ UrlBox::UrlBox()
     set_auto_focusable(false);
 }
 
-UrlBox::~UrlBox()
-{
-}
-
 void UrlBox::focusout_event(GUI::FocusEvent& event)
 {
     set_focus_transition(true);