message: fix a bug in RemoveAttribute that accidentally uses GetVariableMap
  That originated as copy&paste error, I presume.
diff: @@ -208,8 +208,8 @@ bool IO::RemoveAttribute(const std::string &name) noexcept
  #define declare_type(T) \
  else if (type == helper::GetType<T>()) \
  { \
  - auto variableMap = GetVariableMap<T>(); \
  - variableMap.erase(index); \
  + auto attributeMap = GetAttributeMap<T>(); \
  + attributeMap.erase(index); \
  isRemoved = true; \
  }
  ADIOS2_FOREACH_ATTRIBUTE_STDTYPE_1ARG(declare_type)
  