Replace references to cron.update_migration_post_id with cron.update_migration_poster_id in docs (#11068)

Across several files, references to cron.update_migration_post_id are made, although the actual setting is called cron.update_migration_poster_id according to modules/setting/cron.go (https://github.com/go-gitea/gitea/blob/10e2f291442fdc7efc31c02f5ffcba79a36db9ac/modules/setting/cron.go#L54).

Co-authored-by: Antoine GIRARD <sapk@users.noreply.github.com>

Author: kbadk

custom/conf/app.ini.sample

@@ -853,7 +853,7 @@ SCHEDULE = @every 24h
 UPDATE_EXISTING = true
 
 ; Update migrated repositories' issues and comments' posterid, it will always attempt synchronization when the instance starts.
-[cron.update_migration_post_id]
+[cron.update_migration_poster_id]
 ; Interval as a duration between each synchronization. (default every 24h)
 SCHEDULE = @every 24h
 

docs/content/doc/advanced/config-cheat-sheet.en-us.md

@@ -541,7 +541,7 @@ NB: You must `REDIRECT_MACARON_LOG` and have `DISABLE_ROUTER_LOG` set to `false`
 - `RUN_AT_START`: **true**: Run repository statistics check at start time.
 - `SCHEDULE`: **@every 24h**: Cron syntax for scheduling repository statistics check.
 
-### Cron - Update Migration Poster ID (`cron.update_migration_post_id`)
+### Cron - Update Migration Poster ID (`cron.update_migration_poster_id`)
 
 - `SCHEDULE`: **@every 24h** : Interval as a duration between each synchronization, it will always attempt synchronization when the instance starts.
 

docs/content/doc/advanced/config-cheat-sheet.zh-cn.md

@@ -225,7 +225,7 @@ test01.xls: application/vnd.ms-excel; charset=binary
 - `RUN_AT_START`: 是否启动时自动运行仓库统计。
 - `SCHEDULE`: 仓库统计时的Cron 语法，比如：`@every 24h`.
 
-### Cron - Update Migration Poster ID (`cron.update_migration_post_id`)
+### Cron - Update Migration Poster ID (`cron.update_migration_poster_id`)
 
 - `SCHEDULE`: **@every 24h** : 每次同步的间隔时间。此任务总是在启动时自动进行。