[doc] Add trim_tailing_spaces_for_external_table_query variable to the docs.

docs/en/advanced/variables.md

@@ -501,3 +501,7 @@ Translated with www.DeepL.com/Translator (free version)
 * `enable_infer_predicate`
 
   Used to control whether predicate deduction is performed. There are two values: true and false. It is turned off by default, and the system does not perform predicate deduction, and uses the original predicate for related operations. When set to true, predicate expansion occurs.
+
+* `trim_tailing_spaces_for_external_table_query`
+
+  Used to control whether trim the tailing spaces while quering Hive external tables. The default is false.

docs/zh-CN/advanced/variables.md

@@ -488,3 +488,7 @@ SELECT /*+ SET_VAR(query_timeout = 1, enable_partition_cache=true) */ sleep(3);
 - `enable_infer_predicate`
 
   用于控制是否进行谓词推导。取值有两种：true 和 false。默认情况下关闭，系统不在进行谓词推导，采用原始的谓词进行相关操作。设置为 true 后，进行谓词扩展。
+
+- `trim_tailing_spaces_for_external_table_query`
+
+  用于控制查询Hive外表时是否过滤掉字段末尾的空格。默认为false。