Cleanup: Don't use string literals when character literals are needed

src/commands/CmdPrepend.cpp

@@ -118,7 +118,7 @@ int CmdPrepend::execute (std::string&)
     }
     else
     {
-      std::cout << STRING_CMD_PREPEND_NO << "\n";
+      std::cout << STRING_CMD_PREPEND_NO << '\n';
       rc = 1;
       if (_permission_quit)
         break;