ubi8 -> ubi9

Author: sbernauer

.github/ISSUE_TEMPLATE/release.md

@@ -101,7 +101,7 @@ Marketing tasks can now reference published documentation.
 ### Post-release tasks
 - [ ] Bump Rust version. This can be done [in this file](https://github.com/stackabletech/operator-templating/blob/main/config/rust.yaml) by changing `rust_version` and also for the ubi base image [here](https://github.com/stackabletech/docker-images/blob/main/ubi8-rust-builder/Dockerfile#L25). Please be aware that this action will change it for all repositories at the same time (when merging the templating PRs).
 - [ ] Check/bump versions of kube-rs and k8s-openapi (also checking the version of k8s we build against)
-- [ ] Check/bump ubi8 base image
+- [ ] Check/bump ubi9 base image
 - [ ] preflight now checks automatically it's own version and only runs if latest ~~Check/bump preflight~~
 - [ ] Openshift certification. Create an issue from this [template](https://github.com/stackabletech/issues/blob/main/.github/ISSUE_TEMPLATE/olm_manifests.md) for the OLM manifests
 - [ ] Define product versions to include in the next release