## What changes were proposed in this pull request?
We changed our non-standard syntax for `trim` function in #24902 from `TRIM(trimStr, str)` to `TRIM(str, trimStr)` to be compatible with other databases. This pr update the migration guide.
I checked various databases(PostgreSQL, Teradata, Vertica, Oracle, DB2, SQL Server 2019, MySQL, Hive, Presto) and it seems that only PostgreSQL and Presto support this non-standard syntax.
**PostgreSQL**:
```sql
postgres=# select substr(version(), 0, 16), trim('yxTomxx', 'x');
substr | btrim
-----------------+-------
PostgreSQL 11.3 | yxTom
(1 row)
```
**Presto**:
```sql
presto> select trim('yxTomxx', 'x');
_col0
-------
yxTom
(1 row)
```
## How was this patch tested?
manual tests
Closes#24948 from wangyum/SPARK-28093-FOLLOW-UP-DOCS.
Authored-by: Yuming Wang <yumwang@ebay.com>
Signed-off-by: Dongjoon Hyun <dhyun@apple.com>
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