message: doc: Remove "temporary file" notice from 0.17.0 release notes
  not that temporary anymore
  Tree-SHA512:
diff: -(note: this is a temporary file, to be added-to by anybody, and moved to
  -release-notes at release time)
  -
  Bitcoin Core version 0.17.0 is now available from:
  <https://bitcoincore.org/bin/bitcoin-core-0.17.0/>
  