deploydocs default to devbranch="master", although github default branch is main now.

[lrnv]

Everything is in the title. I dont know if you want to fix this, as the switch to main instead of master is quite recent.

Just to give you a heads'up :)

[KristofferC]

Dup of #1443 :)

[andreasvarga]

Sorry for interfering in this discusion, but recently I faced this problem with a new repository. While the deploydocs failed, other issues have been correctly handled by github, by using for master, if not existing, automatically main.
I wonder if this strategy could also be adopted for deploydocs, for which main is now the natural candidate as default. So, master can be automatically used in the case main is not present.