azure-pipelines: explicitly set branch/pr triggers
azure-pipelines: explicitly set branch/pr triggers

It's currently broken, see https://status.dev.azure.com/_event/179641421
and this is the suggested workaround.

Alexpux/MSYS2-packages,atom2013/MSYS2-packages,Alexpux/MSYS2-packages,atom2013/MSYS2-packages,JPeterMugaas/MSYS2-packages,waterlan/MSYS2-packages,juergenpf/MSYS2-packages,mashir43/MSYS2-packages,mati865/MSYS2-packages,mashir43/MSYS2-packages,waterlan/MSYS2-packages,mati865/MSYS2-packages,atom2013/MSYS2-packages,mashir43/MSYS2-packages,waterlan/MSYS2-packages,mashir43/MSYS2-packages,juergenpf/MSYS2-packages,JPeterMugaas/MSYS2-packages,juergenpf/MSYS2-packages,mati865/MSYS2-packages,JPeterMugaas/MSYS2-packages,Alexpux/MSYS2-packages,JPeterMugaas/MSYS2-packages,mati865/MSYS2-packages,atom2013/MSYS2-packages,waterlan/MSYS2-packages,juergenpf/MSYS2-packages,juergenpf/MSYS2-packages,Alexpux/MSYS2-packages