Update num-bigint to 0.4.3

Test: cd external/rust/crates && atest --host -c
Change-Id: I51eaa561a1cfa983aaf0951b05db1a980af45b3a
diff --git a/Cargo.toml b/Cargo.toml
index 54ccc1d..1c15d09 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -3,17 +3,16 @@
 # When uploading crates to the registry Cargo will automatically
 # "normalize" Cargo.toml files for maximal compatibility
 # with all versions of Cargo and also rewrite `path` dependencies
-# to registry (e.g., crates.io) dependencies
+# to registry (e.g., crates.io) dependencies.
 #
-# If you believe there's an error in this file please file an
-# issue against the rust-lang/cargo repository. If you're
-# editing this file be aware that the upstream Cargo.toml
-# will likely look very different (and much more reasonable)
+# If you are reading this file be aware that the original Cargo.toml
+# will likely look very different (and much more reasonable).
+# See Cargo.toml.orig for the original contents.
 
 [package]
 edition = "2018"
 name = "num-bigint"
-version = "0.4.2"
+version = "0.4.3"
 authors = ["The Rust Project Developers"]
 build = "build.rs"
 exclude = ["/bors.toml", "/ci/*", "/.github/*"]