cleanup: remove unused value_proxy/ignore_proxy

include/iterator/detail/arrow_proxy.h

@@ -11,35 +11,4 @@ template <typename Reference> struct arrow_proxy {
 };
 
 template <typename R> arrow_proxy(R r) -> arrow_proxy<R>;
-
-template <typename Value> struct value_proxy {
-  value_proxy operator=(Value && value) {
-    this->value = std::move(value);
-    return *this;
-  }
-
-  operator Value const &() const { return value; }
-  Value const & get() const { return value; }
-
-  Value value;
-};
-
-template <typename Value> struct value_proxy<Value &> {
-  value_proxy operator=(Value & value) {
-    this->value = &value;
-    return *this;
-  }
-
-  operator Value &() const { return *value; }
-  Value & get() const { return *value; }
-
-  Value * value;
-};
-
-struct ignore_proxy {
-  template <typename Value> decltype(auto) operator=(Value && value) {
-    return std::forward<Value>(value);
-  }
-};
-
 }