libweston: Advertise minor version 2 of zwp_linux_explicit_synchronization_v1

Although we already supported minor version 2 of the explicit sync
protocol, we couldn't advertise it previously, since it was not in any
released version of wayland-protocols. With the release of
wayland-protocols 1.18, which includes minor version 2 of this protocol,
and the recent update in weston to require 1.18, we can now safely
advertise minor version 2.

Signed-off-by: Alexandros Frantzis <alexandros.frantzis@collabora.com>
diff --git a/tests/linux-explicit-synchronization-test.c b/tests/linux-explicit-synchronization-test.c
index a89b252..7ef122c 100644
--- a/tests/linux-explicit-synchronization-test.c
+++ b/tests/linux-explicit-synchronization-test.c
@@ -56,11 +56,11 @@
 	}
 
 	assert(global_sync);
-	assert(global_sync->version == 1);
+	assert(global_sync->version == 2);
 
 	sync = wl_registry_bind(
 			client->wl_registry, global_sync->name,
-			&zwp_linux_explicit_synchronization_v1_interface, 1);
+			&zwp_linux_explicit_synchronization_v1_interface, 2);
 	assert(sync);
 
 	return sync;