Fix Typo in the _index.md (grafana#11242)

**What this PR does / why we need it**:

Fixing the small typo in the provided example
[here](https://grafana.com/docs/loki/latest/setup/install/helm/configure-storage/#configure-storage).
This PR just updates the doc.

**Which issue(s) this PR fixes**:
Fixes #<issue number>

**Special notes for your reviewer**:

**Checklist**
- [x] Reviewed the
[`CONTRIBUTING.md`](https://github.com/grafana/loki/blob/main/CONTRIBUTING.md)
guide (**required**)
- [ ] Documentation added
- [ ] Tests updated
- [ ] `CHANGELOG.md` updated
- [ ] If the change is worth mentioning in the release notes, add
`add-to-release-notes` label
- [ ] Changes that require user attention or interaction to upgrade are
documented in `docs/sources/setup/upgrade/_index.md`
- [ ] For Helm chart changes bump the Helm chart version in
`production/helm/loki/Chart.yaml` and update
`production/helm/loki/CHANGELOG.md` and
`production/helm/loki/README.md`. [Example
PR](grafana@d10549e)
- [ ] If the change is deprecating or removing a configuration option,
update the `deprecated-config.yaml` and `deleted-config.yaml` files
respectively in the `tools/deprecated-config-checker` directory.
[Example
PR](grafana@0d4416a)

Co-authored-by: Michel Hollands <[email protected]>

docs/sources/setup/install/helm/configure-storage/_index.md

@@ -46,7 +46,7 @@ This guide assumes Loki will be installed in one of the modes above and that a `
    ```
    serviceAccount:
      annotations:
-       "eks.amazonaws.com/role-arn": "arn:aws:iam::<account id>:role/<role name>:
+       "eks.amazonaws.com/role-arn": "arn:aws:iam::<account id>:role/<role name>"
    ```
 
 3. Configure the storage: