bootstrap.sh: Remove unused unused command.
bootstrap.sh: Remove unused unused command.

The deprecated `unused` command has been removed from the source
repository, so this now fails. We no longer use `unused` so we can just
drop the line that tries to install it.

Signed-off-by: Anthony Yeh <1cdc736ba6fd89dd9b69239aea62ddb9fd1482b1@planetscale.com>

davygeek/vitess,vitessio/vitess,enisoc/vitess,enisoc/vitess,enisoc/vitess,tinyspeck/vitess,mahak/vitess,vitessio/vitess,vitessio/vitess,mahak/vitess,vitessio/vitess,davygeek/vitess,vitessio/vitess,enisoc/vitess,enisoc/vitess,vitessio/vitess,tinyspeck/vitess,davygeek/vitess,davygeek/vitess,vitessio/vitess,tinyspeck/vitess,mahak/vitess,tinyspeck/vitess,tinyspeck/vitess,davygeek/vitess,mahak/vitess,davygeek/vitess,mahak/vitess,davygeek/vitess,mahak/vitess,mahak/vitess,tinyspeck/vitess,tinyspeck/vitess,vitessio/vitess,mahak/vitess,enisoc/vitess,enisoc/vitess