mesa-demos: packageconfig weston should have a dependency on wayland-protocols

mesa-demos: packageconfig weston should have a dependency on wayland-protocols

wayland-protocols is a required depency of mesa-demos when the 'wayland'
packageconfig option is enabled. Usually this doesn't lead to a build
failure because mesa itself depends on wayland-protocols, but when using
other graphics drivers this can cause the following build falure:

| ../mesa-demos-8.5.0/meson.build:69:2: ERROR: Dependency "wayland-protocols" not found, tried pkgconfig
| ERROR: meson failed

Signed-off-by: Carlos Alberto Lopez Perez <clopez@igalia.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
(cherry picked from commit 89615b56899eed7b5c6ad731e2168d99a30fba6c)
Signed-off-by: Steve Sakoman <steve@sakoman.com>