Use correct plugin name for fluentbit ecs task (#11127)

**What this PR does / why we need it**:
Currently the docs suggest using the `loki` output plugin, however the
options provided align with the `grafana-loki` plugin

**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](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/send-data/promtail/cloud/ecs/_index.md

@@ -130,7 +130,7 @@ The `log_router` container image is the [Fluent bit Loki docker image][fluentbit
     "logConfiguration": {
         "logDriver": "awsfirelens",
         "options": {
-            "Name": "loki",
+            "Name": "grafana-loki",
             "Url": "https://<userid>:<grafancloud apikey>@<grafanacloud host>/loki/api/v1/push",
             "Labels": "{job=\"firelens\"}",
             "RemoveKeys": "container_id,ecs_task_arn",