nessie-gc truncate table to avoid increasing storage of DB

[BerkanDemirtas]

In case of using relational database for nessie-gc, nessie-gc keeps data of older runs inside tables and after some runs that cause storage problem(which is caused by data and index storage).
That truncate step will help us to delete these data from these tables:

•      "gc_live_sets"
  

•      "gc_live_set_contents"
  

•     "gc_live_set_content_locations"
  

•     "gc_file_deletions"
  

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[dimas-b]

@BerkanDemirtas Thanks for your contribution! Unfortunately it looks like the author of the commit is not known to GH, which causes the CLA issue noted above. Would you mind amending your commit to set the author according to you GH profile and then sign the CLA? Thx!