chore(helm): update image ghcr.io/linuxserver/grav digest to 4220a4d (#29481)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
|
[ghcr.io/linuxserver/grav](https://redirect.github.com/linuxserver/docker-grav/packages)
([source](https://redirect.github.com/linuxserver/docker-grav)) | digest
| `8acb685` -> `4220a4d` |

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charts/stable/grav/Chart.yaml

@@ -36,4 +36,4 @@ sources:
   - https://github.com/linuxserver/docker-grav
   - https://github.com/truecharts/charts/tree/master/charts/stable/grav
 type: application
-version: 13.2.7
+version: 13.2.8

charts/stable/grav/values.yaml

@@ -1,7 +1,7 @@
 image:
   repository: ghcr.io/linuxserver/grav
   pullPolicy: IfNotPresent
-  tag: 1.7.48@sha256:8acb6858d2d83333e89472779650928d7f21123864316310f8272f8d901c8db6
+  tag: 1.7.48@sha256:4220a4d60e8b27fcfcab649a79ffce0fface7c3d00b8b79197ace43afb809783
 service:
   main:
     ports: