release notes: remove duplicate notes (#15217)

[ti-chi-bot]

This is an automated cherry-pick of #15217

What is changed, added or deleted? (Required)

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

• [dr-autosync] pitr checkpoint ts lag up to 15min after down backup dc  tikv/tikv#15279 and PITR checkpoint lag > 10min during tikv rolling restart tikv/tikv#13638 were fixed in v6.5.4. This PR removes duplicate note in v6.5.5
• Seems region leaders can lose after one tikv instance fail tikv/tikv#14547 was fixed in v6.5.3
  Tips for choosing the affected version(s):

By default, CHOOSE MASTER ONLY so your changes will be applied to the next TiDB major or minor releases. If your PR involves a product feature behavior change or a compatibility change, CHOOSE THE AFFECTED RELEASE BRANCH(ES) AND MASTER.

For details, see tips for choosing the affected versions (in Chinese).

• master (the latest development version)
• v7.5 (TiDB 7.5 versions)
• v7.4 (TiDB 7.4 versions)
• v7.3 (TiDB 7.3 versions)
• v7.1 (TiDB 7.1 versions)
• v6.5 (TiDB 6.5 versions)
• v6.1 (TiDB 6.1 versions)
• v5.4 (TiDB 5.4 versions)
• v5.3 (TiDB 5.3 versions)
• v5.2 (TiDB 5.2 versions)
• v5.1 (TiDB 5.1 versions)
• v5.0 (TiDB 5.0 versions)

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

• This PR is translated from: release notes: remove duplicate notes docs-cn#15331
• 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

[Oreoxmt]

/approve

[ti-chi-bot]

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