Bug#754160: gnutls28: wrong GPL version in debian/copyright

[Jakub Wilk]

Source: gnutls28
Version: 3.2.15-2

debian/copyright reads: "to be able to use and link against libgnutls a 
program needs to be available under a license compatible with LGPLv3+ or 
GPLv2.1+ since GnuTLS requires nettle which requires GMP. GMP (>= 6.0.0) 
is dual licensed LGPLv3+ or GPLv2.1+."

But version 2.1 of GPL doesn't exist
Please make it s/v2\.1/v2/g.

-- 
Jakub Wilk