Bump version requirement for futures-util

opentelemetry-sdk apparently is not getting checked for minimal
versions upstream, and now depends on a Stream export in the root
of futures-util that didn't exist in early versions of that crate.
Require 0.3.17, which appears to be the version that introduced
the top-level re-exports.

Author: djc

Cargo.toml

@@ -47,7 +47,7 @@ opentelemetry-jaeger = "0.21.0"
 opentelemetry-stdout = { version = "0.3.0", features = ["trace", "metrics"] }
 opentelemetry-otlp = { version = "0.15.0", features = ["metrics"] }
 opentelemetry-semantic-conventions = "0.14.0"
-futures-util = { version = "0.3", default-features = false }
+futures-util = { version = "0.3.17", default-features = false }
 tokio = { version = "1", features = ["full"] }
 tokio-stream = "0.1"
 tracing = { version = "0.1.35", default-features = false, features = ["std", "attributes"] }