build: set the default branch of the ephemeral repo for publishing build artifacts to main (#45974)
build: set the default branch of the ephemeral repo for publishing build artifacts to main (#45974)

It looks like because the primary branch for our ephemeral repos doesn't match the build repos
we are pushing to it causes errors around shallow clones.  This attempts to prevent this.

PR Close #45974

gkalpak/angular,gnomeontherun/angular,angular-indonesia/angular,JiaLiPassion/angular,angular/angular,angular/angular,JiaLiPassion/angular,angular-indonesia/angular,angular-indonesia/angular,gnomeontherun/angular,gnomeontherun/angular,gkalpak/angular,angular/angular,gnomeontherun/angular,JiaLiPassion/angular,gkalpak/angular,angular/angular,JiaLiPassion/angular,gkalpak/angular,angular-indonesia/angular