[Koha] koha-manual switched to "main"

[Jonathan Druart]

Hello,

Most of you can ignore this email, but if you have the koha-manual git
repository cloned somewhere locally, you will need to switch to the "main"
branch (instead of "master").

You can simply run the following command (when at the root of koha-manual)
  % git config init.defaultBranch main

Regards,
Jonathan