Fix dns-port in network-policy (#8733)

**What this PR does / why we need it**:
Currently the port for DNS is hardcoded in the network policy which
causes problems in our setup because we use a different port for this.
However, since the coredns pod always names the port "dns" we could use
this name.

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

**Special notes for your reviewer**:

**Checklist**
- [x] Reviewed the
[`CONTRIBUTING.md`](https://github.com/grafana/loki/blob/main/CONTRIBUTING.md)
guide (**required**)
- [ ] Documentation added
- [ ] Tests updated
- [x] `CHANGELOG.md` updated
- [ ] Changes that require user attention or interaction to upgrade are
documented in `docs/sources/upgrading/_index.md`

Co-authored-by: Travis Patterson <travis.patterson@grafana.com>

production/helm/loki/CHANGELOG.md

@@ -13,6 +13,8 @@ Entries should include a reference to the pull request that introduced the chang
 
 [//]: # (<AUTOMATED_UPDATES_LOCATOR> : do not remove this line. This locator is used by the CI pipeline to automatically create a changelog entry for each new Loki release. Add other chart versions and respective changelog entries bellow this line.)
 
+- [BUGFIX] Fix dns port in network-policy
+
 ## 4.10.0
 
 - [CHANGE] Changed version of Grafana Enterprise Logs to v1.6.3

production/helm/loki/templates/networkpolicy.yaml

@@ -33,7 +33,7 @@ spec:
       {{- include "loki.selectorLabels" . | nindent 6 }}
   egress:
     - ports:
-        - port: 53
+        - port: dns
           protocol: UDP
       to:
         - namespaceSelector: {}