test code issues: stability.go, version # is hardcoded, and not test against build since 6.5, please fix it.

[JasonWu0506]

Bug Report

What version of Kubernetes are you using?

What version of TiDB Operator are you using?

What storage classes exist in the Kubernetes cluster and what are used for PD/TiKV pods?

What's the status of the TiDB cluster pods?

What did you do?

What did you expect to see?

What did you see instead?

[JasonWu0506]

/assign @csuzhangxc

[JasonWu0506]

/assign @azurezyq

[csuzhangxc]

stability.go is not enabled currently. And the version upgrade for TiDB is tested in tidbcluster.go, and the version upgrade for TiDB Operator itself is tested in serial.go.