tikv config: hibernate region GA

[CharLotteiu]

What is changed, added or deleted? (Required)

Hibernate region is enabled by default since v5.0.2. Remove experimental warning for hibernate region and update default value.

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

• master (the latest development version)
• v5.1 (TiDB 5.1 versions)
• v5.0 (TiDB 5.0 versions)
• v4.0 (TiDB 4.0 versions)
• v3.1 (TiDB 3.1 versions)
• v3.0 (TiDB 3.0 versions)
• v2.1 (TiDB 2.1 versions)

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

• This PR is translated from: tikv config: hibernate region GA docs-cn#6397
• Other reference link(s):

Do your changes match any of the following descriptions?

• Delete files
• Change aliases
• Need modification after applied to another branch
• Might cause conflicts after applied to another branch

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[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• TomShawn

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[TomShawn]

/remove-status LGT1
/status LGT2

[TomShawn]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: e9796aa

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #5806.