update-wireguard-4.18.4

updated wireguard-postmarketos-stable from 4.14 to 4.18

I:

1. Edited APKBUILD

• updated kernel version
• updated link to newer wireguard version

2. updated checksum
3. built (successful)

• should work
• haven't tested on my device, as I don't know how without installing from apk repo.