chore(pingcap/tidb): bump go version to v1.21.0

[hawkingrei]

Go v1.21.0 was release, we need to upgrade the CI/CD container image to adjust for pingcap/tidb repo.

[ti-chi-bot]

I have already done a preliminary review for you, and I hope to help you do a better job.
Summary:

This pull request upgrades the Go version from 1.20 to 1.21. It updates the image for various containers and pods with the new version.

Potential Problems:

It's hard to find potential problems in this pull request because it's a simple upgrade. However, it's important to check if any of the dependencies or the codebase is incompatible with the new version of Go.

Fixing Suggestions:

The author has already updated the images and containers in the codebase. However, it's recommended to test the application thoroughly to make sure everything is working as expected with the new version of Go.

[ti-chi-bot]

I have already done a preliminary review for you, and I hope to help you do a better job.
This pull request upgrades the Go version from 1.20 to 1.21 in various files, replacing the previous image tags with new ones. The changes seem straightforward and there are no potential problems that stand out.

One suggestion for improvement would be to add a description to the pull request, explaining the reason for the upgrade and any benefits it may provide.

[wuhuizuo]

/lgtm
/approve

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: wuhuizuo

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Needs approval from an approver in each of these files:

• jenkins/OWNERS [wuhuizuo]
• pipelines/OWNERS [wuhuizuo]
• staging/OWNERS [wuhuizuo]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-08-09 02:11:56.679671736 +0000 UTC m=+78681.228687720: ☑️ agreed by wuhuizuo.