Changed tidb_partition_prune_mode default from 'static' to 'dynamic'

[mjonss]

What is changed, added or deleted? (Required)

Reflect the change of default of tidb_partition_prune_mode from static to dynamic.

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• v6.3 (TiDB 6.3 versions)
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• v5.4 (TiDB 5.4 versions)
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What is the related PR or file link(s)?

• This PR is translated from:
• Other reference link(s): sessionctx: Change default tidb_partition_prune_mode from static to dynamic tidb#37712

Do your changes match any of the following descriptions?

• Delete files
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• 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:

• TomShawn
• Yisaer

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[shichun-0415]

/rebase

[shichun-0415]

LGTM

[shichun-0415]

/merge

[ti-chi-bot]

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

Commit hash: 4ad1d85