Remove networking-generic-switch jobs
Remove networking-generic-switch jobs

n-g-s has moved devstack-based zuul3 job definitions in-tree,
remove those from general config.

Depends-On: I584d9be6580ec7641f9268fbbc084c706cb45fbc
Change-Id: I2c0fc94989d89a553aa8f8771ae23a5cffab515c

openstack-infra/project-config,openstack-infra/project-config