Update rancher/k3s-upgrade Docker tag to v1.34.1 (#229)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

build/docker/k3s-upgrade/Dockerfile

@@ -1 +1 @@
-FROM rancher/k3s-upgrade:v1.31.4-k3s1
+FROM rancher/k3s-upgrade:v1.34.1-k3s1