Make it easier to upgrade flux

.gitlab/issue_templates/update_all_components.md

@@ -3,10 +3,10 @@
 Flux and k3s still need manual intervention (see #976 and #993), so we
 only update them on major releases.
 
-* [ ] Update Flux version
+* [ ] Update [Flux version](https://github.com/fluxcd/flux2/releases)
 
-      current_flux_version=0.20.1
-      new_flux_version=0.24.0
+      current_flux_version=$(yq eval .flux.version ansible/group_vars/all/stackspin.yml)
+      new_flux_version=$(curl -s https://api.github.com/repos/fluxcd/flux2/releases/latest | jq -r .name | tr -d 'v')
       sed -i "s/$current_flux_version/$new_flux_version/g" Dockerfile install/flux-version-check.sh docs/installation/install_stackspin.rst ansible/group_vars/all/stackspin.yml
 
 * [ ] Update k3s in `ansible/group_vars/all/stackspin.yml`