No conversion on Date functions when going from SQL Server to PostgreSQL.

**Fully reproducible code snippet**

```
import sqlglot
sql=sqlglot.parse_one('SELECT DAY(FieldDate) FROM t', read='tsql')
sql.sql(dialect='postgres')
```
Results:
'SELECT DAY(FieldDate) FROM t'

Expected results:
'SELECT EXTRACT(DAY FROM FieldDate) FROM t'


**Official Documentation**
https://www.postgresql.org/docs/18/functions-datetime.html#FUNCTIONS-DATETIME-EXTRACT
