Disable Kickstart remediation in partition_for_boot

In rule partition_for_boot the kickstart remediation conflicts with
`bootprot --kickstart` command which we use in the generated kickstart
by default. This causes problems in some profiles for example RHEL 8
ANSSI where this conflict breaks the installation. We can disable
this remediation for this rule because the creation of the partition
is handled by the `bootprot --kickstart` command.

linux_os/guide/system/software/disk_partitioning/partition_for_boot/rule.yml

@@ -31,3 +31,5 @@ template:
     vars:
         mountpoint: /boot
         min_size: 1073741824
+    backends:
+        kickstart: "off"