ksonnet: remove usage of already deleted config match_max_concurrent (#…

…10910)

**What this PR does / why we need it**:
remove the usage of already deleted config match_max_concurrent from
loki ksonnet

**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](d10549e)

production/ksonnet/loki/config.libsonnet

@@ -180,7 +180,6 @@
         log_queries_longer_than: '5s',
       },
       frontend_worker: {
-        match_max_concurrent: true,
         grpc_client_config: {
           max_send_msg_size: $._config.grpc_server_max_msg_size,
         },