BR: Update backup-and-restore-tool.md

[toutdesuite]

What is changed, added or deleted? (Required)

Update backup-and-restore-tool.md

Which TiDB version(s) do your changes apply to? (Required)

• master (the latest development version)
• v4.0 (TiDB 4.0 versions)
• v3.1 (TiDB 3.1 versions)
• v3.0 (TiDB 3.0 versions)
• v2.1 (TiDB 2.1 versions)

If you select two or more versions from above, to trigger the bot to cherry-pick this PR to your desired release version branch(es), you must add corresponding labels such as needs-cherry-pick-4.0, needs-cherry-pick-3.1, needs-cherry-pick-3.0, and needs-cherry-pick-2.1.

What is the related PR or file link(s)?

• This PR is translated from: br: add incremental recover/backup. docs-cn#2985, Add some experimental features of br docs-cn#3143, br: add backup and resotre from s3 with BR docs-cn#2802
• Other reference link(s):

[toutdesuite]

@YuJuncen PTAL, thanks
You made the following change in the restore section of br/backup-and-restore-tool.md in https://github.com/pingcap/docs-cn/pull/3143/files

Please double check whether the same change need to be made in the backup section
Since I cannot request your review, I leave a comment here to make sure that you will receive the email~

[yikeke]

Please help review this PR, thanks~ @ran-huang

[YuJuncen]

@YuJuncen PTAL, thanks
You made the following change in the restore section of br/backup-and-restore-tool.md in https://github.com/pingcap/docs-cn/pull/3143/files

Please double check whether the same change need to be made in the backup section
Since I cannot request your review, I leave a comment here to make sure that you will receive the email~

This flag(in fact, all boolean flags), should be used by the form --boolean-flag(make this flag be true) or --boolean-flag=true(make the flag be specified value). --boolean-flag <ture|false> is a misuse and will always make this flag be true.

Either make this flag be --boolean-flag or --boolean-flag=true would be OK, and the original version also works(even it isn't 'right' enough and misleading, because --boolean-flag false will make the flag be true), so change this at backup section too if possible, thanks.

[toutdesuite]

@YuJuncen PTAL, thanks
You made the following change in the restore section of br/backup-and-restore-tool.md in https://github.com/pingcap/docs-cn/pull/3143/files

Please double check whether the same change need to be made in the backup section
Since I cannot request your review, I leave a comment here to make sure that you will receive the email~

This flag(in fact, all boolean flags), should be used by the form --boolean-flag(make this flag be true) or --boolean-flag=true(make the flag be specified value). --boolean-flag <ture|false> is a misuse and will always make this flag be true.

Either make this flag be --boolean-flag or --boolean-flag=true would be OK, and the original version also works(even it isn't 'right' enough and misleading, because --boolean-flag false will make the flag be true), so change this at backup section too if possible, thanks.

Thanks for your detailed explanation. --send-credentials-to-tikv true has been modified in this PR. I' ll update it in the Chinese doc later

[ran-huang]

Some minor edits~

[YuJuncen]

Rest LGTM

[sre-bot]

/run-all-tests

[sre-bot]

cherry pick to release-3.1 in PR #2722

[sre-bot]

cherry pick to release-4.0 in PR #2723