build(deps): update userfaultfd requirement

---
updated-dependencies:
- dependency-name: userfaultfd
  dependency-version: 0.9.0
  dependency-type: direct:production
  dependency-group: vhost
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

vhost-user-backend/Cargo.toml

@@ -15,7 +15,7 @@ postcopy = ["vhost/postcopy", "userfaultfd"]
 [dependencies]
 libc = "0.2.39"
 log = "0.4.17"
-userfaultfd = { version = "0.8.1", optional = true }
+userfaultfd = { version = "0.9.0", optional = true }
 vhost = { path = "../vhost", version = "0.14.0", features = ["vhost-user-backend"] }
 virtio-bindings = { workspace = true }
 virtio-queue = { workspace = true }