Install skarnet dependencies from github.com instead of skarnet.org.

[SaraSmiseth]

Somehow I could not build because wget from skarnet.org failed to download the sources.
I switched it to github.com. The hashes from github are different thats why they are changed. I left the versions as is.

[AndrewSav]

Looks like we updated deps roughly in the same time. Are you happy with me finishing the debian 13 work where deps update will be integrated, or would you like to merge this first? My preference would be to wait for me, since this will save me from re-basing. The test image for debian 13 now is mailserver2/mailserver:debian13-test01 you are welcome to try it. The work so far is https://github.com/AndrewSav/mailserver/tree/dovecot-2.4-debian-13 But I need my second tests PR integrated before I'm ready to submit this one

[AndrewSav]

Side note, the update deps script is zsh, and it turned out that since I moved to debian zsh no longer works for me, so would be good to change that to bash the same time we move from skarnet to github.

[SaraSmiseth]

Ok this can come after your work and I'll make it a bash script.

[SaraSmiseth]

Obsolete