Update ubuntu.md to mitigate possilbe ARM64 issue with installing desktop package on server

[VGerris]

Workaround for possible issue on ARM64 when installing ubuntu-desktop package after server installation with NetworkManager .

Credits:

https://askubuntu.com/questions/1217252/boot-process-hangs-at-systemd-networkd-wait-online/1501504#1501504 and https://www.reddit.com/r/Ubuntu/comments/1cgmgx8/for_anyone_running_ubuntu_2404_through_qemu_vm_on/

other option is to download from : https://cdimage.ubuntu.com/noble/daily-live/20241025/

[baibhavbista]

thanks @VGerris this fix worked for me (writing this also for the sake of anyone reviewing this PR)

The highlighted text also helped, to know when to exactly do the fix

[osy]

Fixed with a3581f52a2fbb7a8499080c9d1577c0ae4d43e01