Fix typos in futures/src/stream.rs documentation
//! Converting JavaScript `AsyncIterator`s to Rust `Stream`s.
//!
-//! Analogous to the promise to future convertion, this module allows the
-//! turing objects implementing the async iterator protocol into `Stream`s
+//! Analogous to the promise to future conversion, this module allows
+//! turning objects implementing the async iterator protocol into `Stream`s
//! that produce values that can be awaited from.
//!
