Drop dead code from Stacks

Stacks is local to this file, and only used in DataFromTransaction, so
it's easy to confirm this code is unused.

Author: Empact

src/script/sign.cpp

@@ -251,18 +251,11 @@ struct Stacks
     std::vector<valtype> script;
     std::vector<valtype> witness;
 
-    Stacks() {}
-    explicit Stacks(const std::vector<valtype>& scriptSigStack_) : script(scriptSigStack_), witness() {}
+    Stacks() = delete;
+    Stacks(const Stacks&) = delete;
     explicit Stacks(const SignatureData& data) : witness(data.scriptWitness.stack) {
         EvalScript(script, data.scriptSig, SCRIPT_VERIFY_STRICTENC, BaseSignatureChecker(), SigVersion::BASE);
     }
-
-    SignatureData Output() const {
-        SignatureData result;
-        result.scriptSig = PushAll(script);
-        result.scriptWitness.stack = witness;
-        return result;
-    }
 };
 }