Update seed-chainstate.sh

[pseudozach]

it was failing with the error below, this should fix it.

chown: missing operand after ‘xxx/stacks-blockchain-docker/persistent-data/mainnet’
Try 'chown --help' for more information.
Error setting file permissions

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[wileyj]

Interesting. i'll have to double check this on a few different OS'es, but i recall trying whoami initially and had some problems with it on a debian based os (i cannot remember which at the moment).

as long as it works on Debian 10/11, looks good to me though!