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/GitCommitSyntaxHighlighter.cpp

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2022, Brian Gianforcaro <bgianf@serenityos.org>
+ * Copyright (c) 2022, the SerenityOS developers.
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -52,8 +53,4 @@ bool GitCommitSyntaxHighlighter::token_types_equal(u64 token1, u64 token2) const
     return static_cast<GUI::GitCommitToken::Type>(token1) == static_cast<GUI::GitCommitToken::Type>(token2);
 }
 
-GitCommitSyntaxHighlighter::~GitCommitSyntaxHighlighter()
-{
-}
-
 }