changelog: update for v5.0.0-beta5

CHANGELOG.md

+# 5.0.0-beta5 (2018-02-26)
+
+### Fixes
+
+- **Orgs** Unable to switch org when too many orgs listed [#10774](https://github.com/grafana/grafana/issues/10774)
+- **Folders** Make it easier/explicit to access/modify folders using the API [#10630](https://github.com/grafana/grafana/issues/10630)
+- **Dashboard** Scrollbar works incorrectly in Grafana 5.0 Beta4 in some cases [#10982](https://github.com/grafana/grafana/issues/10982)
+- **ElasticSearch** Custom aggregation sizes no longer allowed for Elasticsearch [#10124](https://github.com/grafana/grafana/issues/10124)
+- **oauth** Github OAuth with allowed organizations fails to login [#10964](https://github.com/grafana/grafana/issues/10964)
+- **heatmap** Heatmap panel has partially hidden legend [#10793](https://github.com/grafana/grafana/issues/10793)
+- **snapshots** Expired snapshots not being cleaned up [#10996](https://github.com/grafana/grafana/pull/10996)
+
 # 5.0.0-beta4 (2018-02-19)
 
 ### Fixes