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

Allows changing the label name at the canary in the helm chart.

**Which issue(s) this PR fixes**:
Idk, none?

**Special notes for your reviewer**:

This is a very trivial change.

**Checklist**
- [x] Reviewed the
[`CONTRIBUTING.md`](https://github.com/grafana/loki/blob/main/CONTRIBUTING.md)
guide (**required**)
- [x] Documentation added
- [x] Tests updated
- [x] `CHANGELOG.md` updated
- [x] If the change is worth mentioning in the release notes, add
`add-to-release-notes` label
- [x] Changes that require user attention or interaction to upgrade are
documented in `docs/sources/upgrading/_index.md`
- [x] 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](https://github.com/grafana/loki/commit/d10549e3ece02120974929894ee333d07755d213)

---------

Co-authored-by: Michel Hollands <42814411+MichelHollands@users.noreply.github.com>
Co-authored-by: Travis Patterson <travis.patterson@grafana.com>