Libraries: Use default constructors/destructors in LibSQL

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/LibSQL/AST/SyntaxHighlighter.cpp

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2021, Dylan Katz <dykatz@uw.edu>
+ * Copyright (c) 2022, the SerenityOS developers.
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -95,8 +96,4 @@ bool SyntaxHighlighter::token_types_equal(u64 token1, u64 token2) const
     return static_cast<TokenType>(token1) == static_cast<TokenType>(token2);
 }
 
-SyntaxHighlighter::~SyntaxHighlighter()
-{
-}
-
 }