Should remove app.kubernetes.io/version label from label selectors

[anggao]

Report

When upgrade from KEDA v2.0.0 to v2.2.0, we encountered the following issue

Deployment.apps "keda-operator" is invalid: spec.selector: Invalid value: v1.LabelSelector{MatchLabels:map[string]string{"app":"keda-operator", "app.kubernetes.io/part-of":"keda-operator", "app.kubernetes.io/version":"2.2.0"}, MatchExpressions:[]v1.LabelSelectorRequirement(nil)}: field is immutable

Expected Behavior

We should be able to upgrade KEDA without any issue

Actual Behavior

Deployment.apps "keda-operator" is invalid: spec.selector: Invalid value: v1.LabelSelector{MatchLabels:map[string]string{"app":"keda-operator", "app.kubernetes.io/part-of":"keda-operator", "app.kubernetes.io/version":"2.2.0"}, MatchExpressions:[]v1.LabelSelectorRequirement(nil)}: field is immutable

Steps to Reproduce the Problem

1. Install KEDA by https://github.com/kedacore/keda/releases/download/v2.0.0/keda-2.0.0.yaml
2. upgrade KEDA with https://github.com/kedacore/keda/releases/download/v2.2.0/keda-2.2.0.yaml

Logs from KEDA operator

example

KEDA Version

2.1.0

Kubernetes Version

1.18

Platform

Any

Scaler Details

No response

[zroubalik]

Relevant kustomize issue: kubernetes-sigs/kustomize#1009