Hi,
Good question! I dug around and discovered this isn't as easy as it should be. I have found a way to disable the *tracking* of Solr usage statistics and documented it here:
https://wiki.lyrasis.org/display/DSDOC8x/SOLR+Statistics#SOLRStatistics-DisablingTrackingofStatistics
So, if you follow the docs, you can disable all tracking. But, right now, that "Statistics" menu is still going to appear until we find a volunteer to fix that bug. (There are a few possible workarounds mentioned on the bug itself, but they all require code changes)
Tim