dkms packages for rhel/centos have returned

[Jason A. Donenfeld]

Hi folks,

We switched from dkms to elrepo's kmod a while ago. Unfortunately,
while kmod is convenient for some people, it's a disaster for others,
especially for folks using custom kernels. For that reason, Joe will
be maintaining his copr repo again for dkms packages, for el7 and el8.

<https://www.wireguard.com/install/#red-hat-enterprise-linux-8-module-kmod-module-dkms-tools>
has been updated to show both sets of instructions.

Jason