Bump yellow in cursor color

I guess I'm hitting the cursor plane gamma issue now that's recently
been fixed in AMDGPU.

src/niri.rs

@@ -195,7 +195,7 @@ impl Niri {
                     size: (16, 16).into(),
                 },
                 CommitCounter::default(),
-                [1., 0.5, 0., 1.],
+                [1., 0.8, 0., 1.],
             )),
         );