Remove duplicate env var TZ from monitor spec (#5721)

[ti-chi-bot]

This is an automated cherry-pick of #5721

What problem does this PR solve?

Monitor can be created with duplicate environment variable TZ. This is both theoretically a bad thing to do but also practically can trigger some bugs in k8s when it comes to pod GC.

What is changed and how does it work?

Don't add TZ twice in monitor util

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]

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