chore(helm): update image ghcr.io/open-webui/open-webui digest to 28a8242 (#35667)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| ghcr.io/open-webui/open-webui | digest | `c754aa4` -> `28a8242` |

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.

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- [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check
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charts/stable/ollama/Chart.yaml

@@ -38,5 +38,5 @@ sources:
   - https://github.com/truecharts/charts/tree/master/charts/stable/ollama
   - https://hub.docker.com/r/ollama/ollama
 type: application
-version: 7.15.1
+version: 7.15.2
 

charts/stable/ollama/values.yaml

@@ -9,7 +9,7 @@ rocmImage:
 uiImage:
   repository: ghcr.io/open-webui/open-webui
   pullPolicy: IfNotPresent
-  tag: latest@sha256:c754aa4a17875e82a4ff7815979447eade77573ce2686a14975c8bb83a57923b
+  tag: latest@sha256:28a8242c1bb7518b81723ebad12bfb3d464e0a6199a838c6cd71548e077013b0
 
 securityContext:
   container: