Merge pull request #929 from lsst-it/renovate/nexus3-5.x

Update Helm release nexus3 to v5.12.0

Author: jhoblitt

fleet/lib/nexus/fleet.yaml

@@ -9,7 +9,7 @@ helm:
   chart: nexus3
   releaseName: *name
   repo: https://stevehipwell.github.io/helm-charts
-  version: 5.9.1
+  version: 5.12.0
   timeoutSeconds: 60
   waitForJobs: true
   values: