add cron job to delete old actions from database (#15688)

that's a way to save database storage space.

Signed-off-by: a1012112796 <1012112796@qq.com>

custom/conf/app.example.ini

@@ -1145,6 +1145,14 @@ RUN_AT_START = false
 NO_SUCCESS_NOTICE = false
 SCHEDULE = @every 72h
 
+; Delete all old actions from database
+[cron.delete_old_actions]
+ENABLED = false
+RUN_AT_START = false
+NO_SUCCESS_NOTICE = false
+SCHEDULE = @every 168h
+OLDER_THAN = 8760h
+
 [git]
 ; The path of git executable. If empty, Gitea searches through the PATH environment.
 PATH =