update the helm rancher example

[AlphaWong]

Hi,

I find the example states in the helm instance section with some issues.
I update the helm installation example in order to fit the condition.

reference

https://github.com/rancher/rancher/blob/master/chart/templates/issuer-letsEncrypt.yaml#L4

Best,
Alpha

[catherineluse]

@SheilaghM
If this example Helm command changes, we would probably need to make the change in many places of the docs.

The outstanding question is, should we show that the cert manager version should be specified in Helm commands?

[AlphaWong]

@SheilaghM
If this example Helm command changes, we would probably need to make the change in many places of the docs.

The outstanding question is, should we show that the cert manager version should be specified in Helm commands?

The point is that if we do not specify the run-able version. it will hit this logic https://github.com/rancher/rancher/blob/master/chart/templates/issuer-letsEncrypt.yaml#L4
as a new joiner may not check the source code. So I think that we can offer a fixed version number to make the quick start really quick.