migrate-from-mariadb: add note about utf8mb4_uca1400_ai_ci (#22133)

[ti-chi-bot]

This is an automated cherry-pick of #22133

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[gemini-code-assist]

Summary of Changes

Hello @ti-chi-bot, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the documentation for migrating from MariaDB to TiDB by addressing a specific collation incompatibility. It clarifies that TiDB does not support the utf8mb4_uca1400_ai_ci collation, which is a default in newer MariaDB versions, and guides users to use utf8mb4_0900_ai_ci instead, ensuring a smoother migration process for affected users.

Highlights

• Documentation Update: Added a crucial note to the MariaDB migration guide, informing users about TiDB's lack of support for the utf8mb4_uca1400_ai_ci collation, which is the default in MariaDB 11.6 and later versions.
• Collation Guidance: Provided a recommended alternative, utf8mb4_0900_ai_ci, and explained the difference in Unicode Collation Algorithm (UCA) versions between the two collations to aid in successful migrations.

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[gemini-code-assist]

Code Review

This pull request adds a helpful note about an unsupported MariaDB collation. I've suggested a minor wording change to improve the clarity and flow of the new paragraph, making it easier for users to understand.

[hfxsd]

/approve

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: hfxsd

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