added missing futures-util (#7260)

tooling/webdriver/Cargo.lock

@@ -372,6 +372,7 @@ version = "0.1.2"
 dependencies = [
  "anyhow",
  "futures",
+ "futures-util",
  "hyper",
  "pico-args",
  "serde",

tooling/webdriver/Cargo.toml

@@ -17,6 +17,7 @@ rust-version = "1.57"
 anyhow = "1"
 hyper = { version = "0.14", features = [ "client", "http1", "runtime", "server", "stream", "tcp" ] }
 futures = "0.3"
+futures-util = "0.3"
 pico-args = "0.4"
 serde = { version = "1", features = [ "derive" ] }
 serde_json = "1"