Remove network configurations

[ryonakano]

Fixes elementary/default-settings#324

Checklist

• Built an stable ISO from this branch locally and checked we still have Ethernet connection both on the live and installed session as before

Live session:

Installed session:

• Confirmed these removed files are now shipped by default-settings

user@test:~$ dpkg -S /etc/netplan/01-network-manager-all.yml 
elementary-default-settings: /etc/netplan/01-network-manager-all.yml
user@test:~$ dpkg -S /etc/NetworkManager/conf.d/10-globally-managed-devices.conf 
elementary-default-settings: /etc/NetworkManager/conf.d/10-globally-managed-devices.conf
user@test:~$