Put back plpython_unicode_2.out for SQL_ASCII case.

Put back plpython_unicode_2.out for SQL_ASCII case.

This alternative expected output file is required when using SQL_ASCII
as the client and server encoding. The python encoding conversion used to
throw an error on that, but it is now accepted and you get the UTF-8
representation of the string. I thought that case was already covered by
the other expected output files, but the buildfarm says otherwise.

This is only required on REL9_2_STABLE. In 9.1, we explicitly set
client_encoding to UTF-8 to avoid this.