Applications: Use default constructors/destructors

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/Applications/Spreadsheet/CellSyntaxHighlighter.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020, the SerenityOS developers.
+ * Copyright (c) 2020-2022, the SerenityOS developers.
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -55,9 +55,4 @@ void CellSyntaxHighlighter::rehighlight(const Palette& palette)
     }
     m_client->do_update();
 }
-
-CellSyntaxHighlighter::~CellSyntaxHighlighter()
-{
-}
-
 }