Update matching prompt in common boot template

Earlier, we were using an old kernel and rootfs from 18.09.xx.

We've now switched to using a much newer one from v2020, which is where it requires an update of our assumpt login prompts

This fix is a cherry-pick of commit id: 7a5c59f4292dccc5e02416f792fd3d96bc3c1488 which has already been applied in apertis-test-cases> repository against v2021dev3, see tests/apertis-test-cases!188 (merged)

Signed-off-by: Ritesh Raj Sarraf ritesh.sarraf@collabora.com