Define supported archs in package sources file

[patschi]

On some systems I've received a message like doesn't support architecture 'i386' from apt when updating the package sources. (Those are just amd64 boxes, not sure why)

Would anything speak against of forcing arch=amd64 by replacing:

deb [signed-by=/etc/apt/keyrings/blendbyte.gpg] https://apt.blendbyte.net/nginx ...

to:

deb [arch=amd64 signed-by=/etc/apt/keyrings/blendbyte.gpg] https://apt.blendbyte.net/nginx ...