root-disks: Update .gitignore

Author: mpe

root-disks/.gitignore

@@ -1,13 +1,10 @@
 *.gz
+*.sum
 cloud-init-user-data.img
 ubuntu16.04-cloudimg-powerpc.qcow2
-ubuntu16.04-cloudimg-powerpc.qcow2.sum
 ubuntu16.04-cloudimg-ppc64el.qcow2
-ubuntu16.04-cloudimg-ppc64el.qcow2.sum
 ubuntu21.04-cloudimg-ppc64el.qcow2
-ubuntu21.04-cloudimg-ppc64el.qcow2.sum
 ubuntu21.10-cloudimg-ppc64el.qcow2
-ubuntu21.10-cloudimg-ppc64el.qcow2.sum
 fedora34-cloudimg-ppc64le.qcow2
-fedora34-cloudimg-ppc64le.qcow2.sum
+fedora36-cloudimg-ppc64le.qcow2
 debian-sid-powerpc.qcow2