SCIM: box each bulk operation's dispatch, so the crate builds with the redis feature (SCIM-51)

With redis on, bulk()'s future nested past the compiler's query depth
limit. Boxing the per-operation call keeps it shallow; behavior is
unchanged.

crates/scim/src/bulk.rs

@@ -207,7 +207,7 @@ async fn run_one(
         data.to_string().into_bytes()
     };
 
-    match dispatch(ctx, kind, &route, None, &headers, &body).await {
+    match Box::pin(dispatch(ctx, kind, &route, None, &headers, &body)).await {
         Ok(response) => {
             let location = response
                 .body