chore(deps): update container image grafana/grafana-image-renderer to latest@7920f34 by renovate (#20859)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| grafana/grafana-image-renderer | digest | `f0c5f32` -> `7920f34` |

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

<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiIzNy4zMDEuNSIsInVwZGF0ZWRJblZlciI6IjM3LjMwMS41IiwidGFyZ2V0QnJhbmNoIjoibWFzdGVyIiwibGFiZWxzIjpbImF1dG9tZXJnZSIsInVwZGF0ZS9kb2NrZXIvZ2VuZXJhbC9ub24tbWFqb3IiXX0=-->

charts/stable/grafana-image-renderer/Chart.yaml

@@ -34,4 +34,4 @@ sources:
   - https://github.com/truecharts/charts/tree/master/charts/stable/grafana-image-renderer
   - https://hub.docker.com/r/grafana/grafana-image-renderer
 type: application
-version: 5.8.7
+version: 5.8.8

charts/stable/grafana-image-renderer/values.yaml

@@ -1,7 +1,7 @@
 image:
   pullPolicy: IfNotPresent
   repository: grafana/grafana-image-renderer
-  tag: latest@sha256:f0c5f32f3c34deb15b8a86d61e5e1fdcad85d6a847453676d4182da283e679ad
+  tag: latest@sha256:7920f345848c1f90450ac5b94ac0f5e0bf3cc8fa4c667953b123dfc8902ece9b
 persistence: {}
 portal:
   open: