Merge pull request jupyterhub#2683 from jupyterhub/update-chart-grafana

Updates grafana chart to 6.57.4

Author: manics

mybinder/Chart.yaml

@@ -46,7 +46,7 @@ dependencies:
   #       chart v6 requires Helm 3
   #       chart v6.17.1 gives us Grafana v8.2.1
   - name: grafana
-    version: "6.57.2"
+    version: "6.57.4"
     repository: https://grafana.github.io/helm-charts
     condition: grafana.enabled