Update issues.cpp

tests/issues.cpp

@@ -2,6 +2,7 @@
 #include <tl/expected.hpp>
 
 #include <string>
+#include <memory>
 
 using std::string;
 
@@ -191,4 +192,4 @@ TEST_CASE("Issue 129", "[issues.129]") {
   x1 = std::move(y1);
 
   REQUIRE(**x1 == 2);
-}
+}