Fix for Vietnamese UTM 48N projection parameters as reported by Quách Đồng Thắng

Ran this on the srs db:

```sql
update tbl_srs set parameters="+proj=utm +zone=48 +ellps=WGS84 +towgs84=-192.873,-39.382,-111.202,0.00205,0.0005,-0.00335,0.0188 +units=m +no_defs" , noupdate=1 where srid=3405;
select * from tbl_srs where srid=3405;
```