chore: remove spec.from for Backup and spec.to for Restore in example (#5717)

[ti-chi-bot]

This is an automated cherry-pick of #5717

What problem does this PR solve?

remove spec.from for BR backup and .spec.to for BR restore as they are not recommended to use for a long time.

ref pingcap/docs-tidb-operator#2614

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]

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