Revert "Use wayland 1.5 also for cogl 1.16"

This reverts commit c2ab75c47bb3178e4d41fb6289dddbd80f9ce348.
Revert "add back wayland 1.5 for cogl 1.18"

This reverts commit 9c997fe4464752fa8ed6e4eba2c51fe154642366.