inject.sh: remove unnecessary check

we don't handle single images anymore, so we don't
need to check for it at all.

Signed-off-by: Leah Rowe <leah@libreboot.org>

include/inject.sh

@@ -60,8 +60,6 @@ check_release()
 	case "$archivename" in
 	*_src.tar.xz)
 		err "'$archive' is a src archive, silly!" ;;
-	grub_*|seagrub_*|custom_*|seauboot_*|seabios_withgrub_*)
-		err "'$archive' is a ROM image (it must be a tarball)" ;;
 	*.tar.xz) _stripped_prefix="${archivename#*_}"
 		board="${_stripped_prefix%.tar.xz}" ;;
 	*)