Use bitnami/mongodb helm chart

We've met some issues with the MongoDB replicatSet installation mode with Helm like this one and this one.

The issue has been fixed on the Docker Image but requires a change on the Helm Chart.

Due to the deprecation timeline of Helm Chart repository the change has been done on the new repository: https://github.com/bitnami/charts/blob/master/bitnami/mongodb/README.md

We want to use this new Helm Chart, upgrade notes just talk about changing the chart name to install, everything else should be backward compatible.