sql-faq: add missing DELAYED priority (#12237)

[ti-chi-bot]

This is an automated cherry-pick of #12237

What is changed, added or deleted? (Required)

Add the missing DELAYED priority

sql> SELECT HIGH_PRIORITY 1;
+---+
| 1 |
+---+
| 1 |
+---+
1 row in set (0.0014 sec)

sql> SELECT LOW_PRIORITY 1;
+---+
| 1 |
+---+
| 1 |
+---+
1 row in set (0.0004 sec)

sql> SELECT DELAYED 1;
+---+
| 1 |
+---+
| 1 |
+---+
1 row in set (0.0004 sec)

see also: https://github.com/pingcap/tidb/blob/1e0956d5ba41182e603295e02ae8f767d62979e4/distsql/request_builder.go#L257-L267

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

• master (the latest development version)
• v6.6 (TiDB 6.6 versions)
• v6.5 (TiDB 6.5 versions)
• v6.4 (TiDB 6.4 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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[shichun-0415]

/verify

[shichun-0415]

/merge

[ti-chi-bot]

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

Commit hash: 6002358