extensions-ocp-rhel-9.6.yaml: add rhel-9.6-fast-datapath repo

Before we inherited this from the ocp-rhel-9.6 manifest. But now that
we're inheriting from the rhel-9.6 manifest, that repo isn't enabled
by default there since it's not strictly needed (because we don't ship
openvswitch in the base).

So we need to enable it here ourselves.

Author: jlebon

extensions-ocp-rhel-9.6.yaml

@@ -18,6 +18,8 @@ extensions:
       - crun-wasm
   # https://github.com/coreos/fedora-coreos-tracker/issues/1504
   ipsec:
+    repos:
+      - rhel-9.6-fast-datapath
     packages:
       - libreswan
       - NetworkManager-libreswan