Update spin requirement from 0.9.8 to 0.10.0

---
updated-dependencies:
- dependency-name: spin
  dependency-type: direct:production
...

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

Author: dependabot[bot]

futures-util/Cargo.toml

@@ -42,7 +42,7 @@ memchr = { version = "2.2", optional = true }
 futures_01 = { version = "0.1.25", optional = true, package = "futures" }
 tokio-io = { version = "0.1.9", optional = true }
 pin-project-lite = "0.2.6"
-spin = { version = "0.9.8", optional = true }
+spin = { version = "0.10.0", optional = true }
 
 [dev-dependencies]
 futures = { path = "../futures", features = ["async-await", "thread-pool"] }