how to turn off delimiters in generated SQL scripts for data types in SQL Server Management Studio
I don't know of any setting which will do this in SSMS.  Microsoft probably does it so that they don't need to check the data type name for special characters when generating the script (user defined data type names could have anything in them) so they just box everything.

You could submit that as a feature request to the tools team via connect.microsoft.com or to Mladen for including in his SSMS Tools Pack.