fix(helm-chart): update helm release loki to 5.8.7 (#851)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [loki](https://grafana.github.io/helm-charts)
([source](https://togithub.com/grafana/helm-charts)) | patch | `5.8.5`
-> `5.8.7` |

---

### Release Notes

<details>
<summary>grafana/helm-charts (loki)</summary>

###
[`v5.8.7`](https://togithub.com/grafana/helm-charts/releases/tag/helm-loki-5.8.7)

Helm chart for Grafana Loki in simple, scalable mode

Source commit:
grafana/loki@6a1f34f

Tag on source:
https://github.com/grafana/loki/releases/tag/helm-loki-5.8.7

###
[`v5.8.6`](https://togithub.com/grafana/helm-charts/releases/tag/helm-loki-5.8.6)

Helm chart for Grafana Loki in simple, scalable mode

Source commit:
grafana/loki@a24ef7b

Tag on source:
https://github.com/grafana/loki/releases/tag/helm-loki-5.8.6

</details>

---

### Configuration

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

🚦 **Automerge**: Disabled by config. Please merge this manually once you
are satisfied.

♻ **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://togithub.com/renovatebot/renovate).

<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiIzNS4xNDQuMCIsInVwZGF0ZWRJblZlciI6IjM1LjE0NC4zIiwidGFyZ2V0QnJhbmNoIjoibWFpbiJ9-->

Co-authored-by: greyrock-bot <1583719+greyrock-bot[bot]@users.noreply.github.com>

kubernetes/greyrock-ops/apps/monitoring/loki/app/helmrelease.yaml

@@ -9,7 +9,7 @@ spec:
   chart:
     spec:
       chart: loki
-      version: 5.8.5
+      version: 5.8.7
       sourceRef:
         kind: HelmRepository
         name: grafana