Removed internal variable with name "data" inside a generated method…

Removed internal variable with name "data" inside a generated method _nested_root(). Local variable with name "data" violates [-Werror=shadow]. (#4587)

src/idl_gen_cpp.cpp

@@ -1645,8 +1645,7 @@ class CppGenerator : public BaseGenerator {
         code_.SetValue("CPP_NAME", TranslateNameSpace(qualified_name));
 
         code_ += "  const {{CPP_NAME}} *{{FIELD_NAME}}_nested_root() const {";
-        code_ += "    auto data = {{FIELD_NAME}}()->Data();";
-        code_ += "    return flatbuffers::GetRoot<{{CPP_NAME}}>(data);";
+        code_ += "    return flatbuffers::GetRoot<{{CPP_NAME}}>({{FIELD_NAME}}()->Data());";
         code_ += "  }";
       }