refactor(notes): scope stacked-note sticky to desktop

Move position: sticky from the global .note rule into the desktop
@media block of the scoped stacked-note components, so mobile no longer
inherits sticky positioning (and no top is set there).

src/components/FluxNote.vue

@@ -211,7 +211,6 @@ $header-height: 40px;
     display: flex;
     flex-direction: column;
     overflow-y: auto;
-    position: sticky;
 
     &:not(:first-child) {
       border-top: 1px solid rgba(18, 19, 58, 0.2);