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/ValueSlider.cpp

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2021, Marcus Nilsson <brainbomb@gmail.com>
+ * Copyright (c) 2022, the SerenityOS developers.
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -67,10 +68,6 @@ ValueSlider::ValueSlider(Gfx::Orientation orientation, String suffix)
     };
 }
 
-ValueSlider::~ValueSlider()
-{
-}
-
 String ValueSlider::formatted_value() const
 {
     return String::formatted("{:2}{}", value(), m_suffix);