bump to v1.6.0-alpha.4

[xhebox]

What problem does this PR solve?

What is changed and how does it work?

Code changes

• Has Go code change
• Has CI related scripts change

Tests

• Unit test
• E2E test
• Manual test
• No code

Side effects

• Breaking backward compatibility
• Other side effects:

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation

Release Notes

Please refer to Release Notes Language Style Guide before writing the release note.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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[codecov-commenter]

Codecov Report

Merging #5221 (31f1703) into master (dabcb4c) will increase coverage by 1.32%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5221      +/-   ##
==========================================
+ Coverage   57.76%   59.08%   +1.32%     
==========================================
  Files         246      249       +3     
  Lines       29479    32815    +3336     
==========================================
+ Hits        17029    19390    +2361     
- Misses      10795    11724     +929     
- Partials     1655     1701      +46     

Flag	Coverage Δ
e2e	27.06% <ø> (?)
unittest	57.76% <ø> (-0.01%)	⬇️

[csuzhangxc]

/test /test pull-e2e-kind
/test pull-e2e-kind-across-kubernetes

[ti-chi-bot]

@csuzhangxc: The label(s) //test, /pull-e2e-kind, /pull-e2e-kind-across-kubernetes cannot be applied, because the repository doesn't have them.

In response to this:

/test /test pull-e2e-kind
/test pull-e2e-kind-across-kubernetes

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.

[ti-chi-bot]

@csuzhangxc: No presubmit jobs available for pingcap/tidb-operator@master

In response to this:

/test /test pull-e2e-kind
/test pull-e2e-kind-across-kubernetes

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[csuzhangxc]

/test pull-e2e-kind-basic

[ti-chi-bot]

@csuzhangxc: The label(s) /pull-e2e-kind-basic cannot be applied, because the repository doesn't have them.

In response to this:

/test pull-e2e-kind-basic

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.

[ti-chi-bot]

@csuzhangxc: No presubmit jobs available for pingcap/tidb-operator@master

In response to this:

/test pull-e2e-kind-basic

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.