Update tiflash-overview.md (#10635)

[ti-chi-bot]

This is an automated cherry-pick of #10635

First-time contributors' checklist

• I've signed Contributor License Agreement that's required for repo owners to accept my contribution.

What is changed, added or deleted? (Required)

Add the description that to deploy TiFlash under the Linux AMD64 architecture, the CPU must support AVX2 instruction sets

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

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.

• master (the latest development version)
• v6.4 (TiDB 6.4 versions)
• v6.3 (TiDB 6.3 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:
• 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

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• shichun-0415

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After your PR has acquired the required number of LGTMs, you can assign this pull request to the committer in the list by filling /assign @committer in the comment to help you merge this pull request.

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[shichun-0415]

/merge

[ti-chi-bot]

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

Commit hash: e3cbfa3