workspace: move back to traits.git/master (#856)

Now RustCrypto/traits#1650 merged the branch
has been removed.

Author: baloo

Cargo.lock

@@ -18,4 +18,4 @@ opt-level = 2
 sec1 = { git = "https://github.com/RustCrypto/formats.git" }
 pkcs8 = { git = "https://github.com/RustCrypto/formats.git" }
 # https://github.com/RustCrypto/traits/pull/1650
-elliptic-curve = { git = "https://github.com/baloo/traits.git", branch = "baloo/elliptic-curve/pkcs8-API-break" }
+elliptic-curve = { git = "https://github.com/RustCrypto/traits.git" }