Update shallow_flash.sh

It affects me when I try to restore my profile. See this message:

### Push Done.
### Restore Profile from /tmp/shallowflashprofile.kj9Dnrvn2KlI
### Waiting for device... please ensure it is connected, switched on and remote debugging is enabled in Gaia
Backup and restore Firefox OS profiles.

Usage:
  -b|--backup	backup user profile.
  -r|--restore	restore user profile.
  --sdcard	also backup/restore SD card.
  --no-reboot	do not reboot B2G after backup/restore.
  -p|--profile-dir	specify the profile folder. Default=./mozilla-profile
  -h|--help	display help.
-p/tmp/shallowflashprofile.kj9Dnrvn2KlI is not a recognized option!
### Removing Profile under /tmp/shallowflashprofile.kj9Dnrvn2KlI