Add num-traits to Cargo.toml/lock

num-traits is already part of vendor/ but wasn't yet
explicitly listed in Cargo.toml.
Added num-traits-0.2.5 to Cargo.toml and ran
fx update-rustc-third-party.

Test=Ran integration test

Change-Id: I90782287b1be593251acf2dddb5ac29a60feb883
diff --git a/rustc_deps/Cargo.lock b/rustc_deps/Cargo.lock
index 93a1dbe..32df591 100644
--- a/rustc_deps/Cargo.lock
+++ b/rustc_deps/Cargo.lock
@@ -535,6 +535,7 @@
  "num 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-bigint 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-derive 0.2.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-traits 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "owning_ref 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "pest 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
diff --git a/rustc_deps/Cargo.toml b/rustc_deps/Cargo.toml
index c97e8b6..aa3e6ce 100644
--- a/rustc_deps/Cargo.toml
+++ b/rustc_deps/Cargo.toml
@@ -45,6 +45,7 @@
 num = "0.2"
 num-derive = "0.2.4"
 num-bigint = { version = "0.2", features = ["rand"] }
+num-traits= "0.2.5"
 owning_ref = "0.4.0"
 parking_lot = "0.7.1"
 pest = "2.1"