Add setup erase command to example for adding more RPMs to the server…

… container (keycloak#23639)

Closes keycloak#23637

docs/guides/server/containers.adoc

@@ -101,7 +101,9 @@ It is possible to install new RPMs if absolutely required, following this two-st
 ----
 FROM registry.access.redhat.com/ubi9 AS ubi-micro-build
 RUN mkdir -p /mnt/rootfs
-RUN dnf install --installroot /mnt/rootfs <package names go here> --releasever 9 --setopt install_weak_deps=false --nodocs -y; dnf --installroot /mnt/rootfs clean all
+RUN dnf install --installroot /mnt/rootfs <package names go here> --releasever 9 --setopt install_weak_deps=false --nodocs -y && \
+    dnf --installroot /mnt/rootfs clean all && \
+    rpm --root /mnt/rootfs -e --nodeps setup
 
 FROM quay.io/keycloak/keycloak
 COPY --from=ubi-micro-build /mnt/rootfs /