chore(helm): update image xwiki digest to c256130 (#28071)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| xwiki | digest | `b9e8f2c` -> `c256130` |

Add the preset `:preserveSemverRanges` to your config if you don't want
to pin your dependencies.

---

### Configuration

📅 **Schedule**: Branch creation - At any time (no schedule defined),
Automerge - At any time (no schedule defined).

🚦 **Automerge**: Enabled.

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the
rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update
again.

---

- [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check
this box

---

This PR has been generated by [Renovate
Bot](https://redirect.github.com/renovatebot/renovate).

<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiIzOC4xMjguMSIsInVwZGF0ZWRJblZlciI6IjM4LjEyOC4xIiwidGFyZ2V0QnJhbmNoIjoibWFzdGVyIiwibGFiZWxzIjpbImF1dG9tZXJnZSIsInJlbm92YXRlL2NvbnRhaW5lciIsInR5cGUvZGlnZXN0Il19-->

charts/stable/xwiki/Chart.yaml

@@ -33,4 +33,4 @@ sources:
   - https://github.com/xwiki/xwiki-docker
   - https://hub.docker.com/_/xwiki
 type: application
-version: 14.6.8
+version: 14.6.9

charts/stable/xwiki/values.yaml

@@ -1,6 +1,6 @@
 image:
   repository: xwiki
-  tag: 16.8.0-postgres-tomcat@sha256:b9e8f2c84ddacf75b5da038f3df258e776b6d745128935663b81859015dff478
+  tag: 16.8.0-postgres-tomcat@sha256:c25613066e400b68bca0f671400ca204dd6e4ed3b4f164cac476fba056ce4d41
   pullPolicy: IfNotPresent
 service:
   main: