fix(system-upgrade): Fix unexpected hard-coded version numbers

infrastructure/system-upgrades/fedora-system-upgrade.yaml

@@ -10,11 +10,11 @@ stringData:
     #!/bin/sh
     set -e
     set -x
-    if grep "Fedora release 37" /etc/fedora-release; then
+    if grep "Fedora release $SYSTEM_UPGRADE_PLAN_LATEST_VERSION" /etc/fedora-release; then
       exit 0
     fi
     systemd-run --same-dir --wait --collect --service-type=exec dnf install -y dnf-plugin-system-upgrade
-    systemd-run --same-dir --wait --collect --service-type=exec dnf system-upgrade download -y --best --releasever=36
+    systemd-run --same-dir --wait --collect --service-type=exec dnf system-upgrade download -y --best --releasever=$SYSTEM_UPGRADE_PLAN_LATEST_VERSION
     systemd-run --same-dir --wait --collect --service-type=exec dnf system-upgrade -y reboot
 ---
 apiVersion: upgrade.cattle.io/v1