Temporarily change branch name to 24.08extra when updating to 24.08 runtime

[bbhtt]

See https://discourse.flathub.org/t/freedesktop-sdk-24-08-0-released/7630/5

com.github.Matoking.protontricks/com.github.Matoking.protontricks.yml

Line 5 in 57efddc

x-gl-versions: &gl-versions 23.08;23.08-extra;1.4

cc @Matoking