I think it is debatable that showing the version of a component is a "vulnerability". Trying to hide it is little more than security by obscurity. That said, sometimes it is far, far easier to just hide the version than convince a stupid vulnerability scanner of its false positives.
To my knowledge, Splunk provides no out-of-the-box way of doing this. If this is necessary, I would recommend filing an Enhancement Request with Splunk support. Describe why this functionality is important to you, as this helps Splunk project management prioritize work.
