v7.5.7: change the default value of tidb_enable_historical_stats (#21551)

Author: Oreoxmt

system-variables.md

@@ -2095,8 +2095,8 @@ mysql> SELECT job_info FROM mysql.analyze_jobs ORDER BY end_time DESC LIMIT 1;
 - Persists to cluster: Yes
 - Applies to hint [SET_VAR](/optimizer-hints.md#set_varvar_namevar_value): No
 - Type: Boolean
-- Default value: `ON`
-- This variable controls whether to enable historical statistics. The default value changes from `OFF` to `ON`, which means that historical statistics are enabled by default.
+- Default value: `OFF`. Before v7.5.7, the default value is `ON`.
+- This variable controls whether to enable historical statistics. The default value is `OFF`, which means that historical statistics are disabled by default.
 
 ### tidb_enable_historical_stats_for_capture