Manifests: disable default ZRAM config

In coreos#2937
we moved zram-generator to the system-configuration.yaml
manifest so it's shared with RHCOS.
However in the centOS stream 9 zram-generator-0.3.2 [1] ships a
default config file, resulting in a swap device being created
by default.
This ends up breaking kubelet, until kubernetes 1.30
is released

[1] https://gitlab.com/redhat/centos-stream/rpms/rust-zram-generator/-/blob/c9s/zram-generator.conf?ref_type=heads

manifests/system-configuration.yaml

@@ -54,3 +54,8 @@ postprocess:
   - |
     #!/usr/bin/env bash
     systemctl mask systemd-repart.service
+  # zram-generator-0.3.2 (shipped in centOS 9) provides a default
+  # zram-generator config, we want to disable it
+  - |
+    #!/usr/bin/env bash
+    rm -f /usr/lib/systemd/zram-generator.conf