remove proc-macro-hack dep

Author: carllerche

async-stream/Cargo.toml

@@ -22,7 +22,6 @@ readme = "README.md"
 [dependencies]
 async-stream-impl = { version = "0.1.0" }
 futures-core-preview = "=0.3.0-alpha.17"
-proc-macro-hack = "0.5.8"
 
 [dev-dependencies]
 tokio = "=0.2.0-alpha.1"