wallet: no need for duplicate storage for ABANDON_HASH constant

src/wallet/wallet.cpp

@@ -324,8 +324,6 @@ std::shared_ptr<CWallet> CreateWallet(interfaces::Chain& chain, const std::strin
     return wallet;
 }
 
-const uint256 CWalletTx::ABANDON_HASH(uint256::ONE);
-
 /** @defgroup mapWallet
  *
  * @{

src/wallet/wallet.h

@@ -275,7 +275,7 @@ private:
     /** Constant used in hashBlock to indicate tx has been abandoned, only used at
      * serialization/deserialization to avoid ambiguity with conflicted.
      */
-    static const uint256 ABANDON_HASH;
+    static constexpr const uint256& ABANDON_HASH = uint256::ONE;
 
 public:
     /**