docs: Update spawn.txt
docs: Update spawn.txt

With the change in process name it's now better to use pkill -f than
killall.

Fix misspellings of receiptomatc.

Signed-off-by: Andrew Clayton <02e0a999c50b1f88df7a8f5a04e1b76b35ea6a88@opentechlabs.co.uk>

ac000/receiptomatic