fix HPA and update apiVersion

[pinoOgni]

Fix issue #66 and update API version to autoscaling/v2

Note: if we leave the {{ name }} in name: {{ include "free5gc-amf.fullname" $ }}-{{ .name }}-hpa the name of the HPA will be something like free5gc-free5gc-amf-amf-hpa with amf repeated twice. Wouldn't it be better to remove it? Almost the same thing is for name: {{ include "free5gc-amf.fullname" $ }}-{{ .name }}.

What do you think?

Thanks to @raoufkh for the advice on the solution!

[raoufkh]

Thanks a lot @pinoOgni!