[release-2.8.x] update changelog for v2.8.6 (#10930)

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

**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)

Author: ashwanthgoli

CHANGELOG.md

@@ -2,6 +2,15 @@
 
 ### All Changes
 
+## 2.8.6 (2023-10-17)
+
+#### Loki
+
+##### Security
+
+* [10887](https://github.com/grafana/loki/pull/10887) upgrade go-grpc to v1.56.3 and golang.org/x/net to v0.17.0 to patch CVE-2023-39325 / CVE-2023-44487
+* [10889](https://github.com/grafana/loki/pull/10889) upgrade go to v1.20.10 to patch CVE-2023-39325 / CVE-2023-44487
+
 ## 2.8.5 (2023-09-14)
 
 #### Loki