message: misc: update deprecation notice in data directories
diff: # DEPRECATED
  -The files in this directory are deprecated and will be deleted on October 31st 2021.
  +Nextclade datasets require frequent update to keep up with evolving diversity and new clade definitions and we no longer provide these as part of this repository.
  +The `tree.json`, `qc.json`, and `primers.csv`, and `tag.json` files in these directories are outdated and will be deleted on October 31st 2021.
  +The stable `reference.fasta`, its annotation `genemap.gff` and example sequences will remain.
  -Instead, use Nextclade datasets feature to download datasets.
  -See [Nextclade CLI](https://docs.nextstrain.org/projects/nextclade/en/latest/user/nextclade-cli.html) documentation for example usage and [Nextclade Datasets](https://docs.nextstrain.org/projects/nextclade/en/latest/user/datasets.html) documentation for more details.
  +To download up-to-date full Nextclade datasets, please see [Nextclade CLI](https://docs.nextstrain.org/projects/nextclade/en/latest/user/nextclade-cli.html) documentation for example usage and [Nextclade Datasets](https://docs.nextstrain.org/projects/nextclade/en/latest/user/datasets.html) documentation for more details.
  