remove version from Helm chart

[meysholdt]

Sometimes people take the helm chart from this repository and try to install Gitpod with it.
That will almost always fail, because the helm chart pulls in the wrong version of the docker images.
Since images and chart are tightly coupled, the chart will only work with the images that were built from the same commit.

It's easy to do this when taking the chart from the installer.

gitpod/chart/values.yaml

Line 4 in e42f7c8

version: 0.6.0-beta5

When using the helm chart from this repository, it should be mandatory to explicitly set the version value.
When using the chart from charts.gitpod.io or the installer, setting version manually is not necessary, because Werft will have ingrained the version into the packaged chart.

There should be a good error message when running helm install gitpod without --set version=