update stub: pharokka/installdatabases

[jen-reeve]

Description of the bug
Per this slack thread it seems that empty .gz files generated by simply touch .gz break the snapshot functionality of nf-test by causing an EOFException because the files are not actually compressed.

Per this comment a fix is to replace the touch command with echo "" | gzip > .gz.

[vagkaratzas]

@jen-reeve can you fix these and push please?