Convert key meta data to utf-8

gpg defaults to latin1 if no locale environment variable specifies
something else. Up until recently the maintainer scripts for the kernel
keyring called gpg in a (nearly) empty environment and thus the meta
data for most keys is latin1 encoded.

Since the script was fixed to use UTF-8 for the meta data, Krzysztof
Wilczyński's certificate (7C64768D3DE334E7) was updated and is UTF-8
encoded now. So currently we have an encoding mixture.

Align all meta data to use UTF-8 encoding.