Another shellcheck warning

[7flying]

Error: SHELLCHECK_WARNING ([CWE-149](https://cwe.mitre.org/data/definitions/149.html)): 
/usr/lib/dracut/modules.d/51coreos-installer/coreos-installer-growfs:32:52: warning[[SC2027](https://github.com/koalaman/shellcheck/wiki/SC2027)]: The surrounding quotes actually unquote this. Remove or escape them.
#   30|   partition=$(grep -c "${device}"[0-9] /proc/partitions)
#   31|   growpart $installation_device $partition
#   32|-> echo "growpart executed on "$installation_device" "$partition" "

on gating; looks innocuous but I would like to see no warnings there

[travier]

See #10 & #11