Fix S3 Helm example (#11180)

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

S3 Helm example uses the wrong keys. See:
cc6f0eca98/production/helm/loki/values.yaml (L280-L281)


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

**Special notes for your reviewer**:

**Checklist**
- [ ] 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](d10549e3ec)
- [ ] 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](0d4416a4b0)

---------

Co-authored-by: J Stickler <julie.stickler@grafana.com>

docs/sources/setup/install/helm/install-monolithic/_index.md

@@ -55,12 +55,15 @@ If you set the `singleBinary.replicas` value to 2 or more, this chart configures
         commonConfig:
           replication_factor: 3
         storage:
+          bucketNames:
+            chunks: loki-chunks
+            ruler: loki-ruler
+            admin: loki-admin
           type: 's3'
           s3:
             endpoint: foo.aws.com
-            bucketnames: loki-chunks
-            secret_access_key: supersecret
-            access_key_id: secret
+            secretAccessKey: supersecret
+            accessKeyId: secret
       singleBinary:
         replicas: 3
       ```