changelog: Fixed wrong link to federation PR.
## 2.18.0 / 2020-05-05
-* [CHANGE] Federation: Only use local TSDB for federation (ignore remote read). #7077
+* [CHANGE] Federation: Only use local TSDB for federation (ignore remote read). #7096
* [CHANGE] Rules: `rule_evaluations_total` and `rule_evaluation_failures_total` have a `rule_group` label now. #7094
* [FEATURE] Tracing: Added experimental Jaeger support #7148
* [ENHANCEMENT] TSDB: Significantly reduce WAL size kept around after a block cut. #7098
