storage.engine gets removed by operator after having been set

Bug Report

What version of Kubernetes are you using?

WARNING: This version information is deprecated and will be replaced with the output from kubectl version --short.  Use --output=yaml|json to get the full version.
Client Version: version.Info{Major:"1", Minor:"25", GitVersion:"v1.25.4", GitCommit:"872a965c6c6526caa949f0c6ac028ef7aff3fb78", GitTreeState:"clean", BuildDate:"2022-11-09T13:36:36Z", GoVersion:"go1.19.3", Compiler:"gc", Platform:"darwin/arm64"}
Kustomize Version: v4.5.7
Server Version: version.Info{Major:"1", Minor:"25", GitVersion:"v1.25.6+k3s1", GitCommit:"9176e03c5788e467420376d10a1da2b6de6ff31f", GitTreeState:"clean", BuildDate:"2023-01-26T00:30:33Z", GoVersion:"go1.19.5", Compiler:"gc", Platform:"linux/arm64"}

What version of TiDB Operator are you using?

NAME         	NAMESPACE 	REVISION	UPDATED                             	STATUS  	CHART               	APP VERSION
tidb-operator	tidb-admin	1       	2023-02-28 23:55:38.903854 -0500 EST	deployed	tidb-operator-v1.4.3	v1.4.3

What did you do?
I just set this in tikv.config

[raftdb]
  max-open-files = 256

[rocksdb]
  max-open-files = 256

[storage]
  reserve-space = "0MB"
  engine: partitioned-raft-kv

What did you expect to see?
I was expecting to see partitioned-raft-kv being set on each tikv pods but it's not in /etc/tikv/tikv.toml

What did you see instead?
Nothing. A few second after having seen my configuration in the k8s object I can see that the operator has removed it

$ k get tidbclusters.pingcap.com -o yaml|yq .'items[].spec.tikv.config'  
[raftdb]
  max-open-files = 256

[rocksdb]
  max-open-files = 256

[storage]
  reserve-space = "0MB"

Reproduce the issue with TiDB Operator v1.4.3 and the shown tikv.config, then inspect the reconciliation that removes storage.engine from the Kubernetes object. Compare the resulting configuration with /etc/tikv/tikv.toml on each TiKV pod. Done means partitioned-raft-kv remains in the object and is rendered into the pod configuration.