Merge #13633: Drop dead code from Stacks

Summary:
5617840 Drop dead code from Stacks (Ben Woosley)

Pull request description:

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

Tree-SHA512: cc680c99f9b31cb56db70f453087d642f83906ce594c07a6bf3e61427cfbee41441495d440b240419ba3386582cf0670c0999b2f51e7fd56b00e0a0f3f618845

Backport of Core PR13633
bitcoin/bitcoin#13633

Test Plan:
  make check

Reviewers: deadalnix, Fabien, jasonbcox, O1 Bitcoin ABC, #bitcoin_abc

Reviewed By: jasonbcox, O1 Bitcoin ABC, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D4726

Author: laanwj

src/script/sign.cpp

@@ -280,19 +280,12 @@ namespace {
 struct Stacks {
     std::vector<valtype> script;
 
-    Stacks() {}
-    explicit Stacks(const std::vector<valtype> &scriptSigStack_)
-        : script(scriptSigStack_) {}
+    Stacks() = delete;
+    Stacks(const Stacks &) = delete;
     explicit Stacks(const SignatureData &data) {
         EvalScript(script, data.scriptSig, MANDATORY_SCRIPT_VERIFY_FLAGS,
                    BaseSignatureChecker());
     }
-
-    SignatureData Output() const {
-        SignatureData result;
-        result.scriptSig = PushAll(script);
-        return result;
-    }
 };
 } // namespace