Update futures-channel to 0.3.21

Test: cd external/rust/crates && atest --host -c
Change-Id: I9c1e17e5ea84d783817d5e69955f4c685e005721
diff --git a/Cargo.toml.orig b/Cargo.toml.orig
index 6bd240c..f356eab 100644
--- a/Cargo.toml.orig
+++ b/Cargo.toml.orig
@@ -1,12 +1,11 @@
 [package]
 name = "futures-channel"
+version = "0.3.21"
 edition = "2018"
-version = "0.3.17"
-authors = ["Alex Crichton <alex@alexcrichton.com>"]
+rust-version = "1.45"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/rust-lang/futures-rs"
 homepage = "https://rust-lang.github.io/futures-rs"
-documentation = "https://docs.rs/futures-channel/0.3"
 description = """
 Channels for asynchronous communication using futures-rs.
 """
@@ -23,8 +22,8 @@
 cfg-target-has-atomic = []
 
 [dependencies]
-futures-core = { path = "../futures-core", version = "0.3.17", default-features = false }
-futures-sink = { path = "../futures-sink", version = "0.3.17", default-features = false, optional = true }
+futures-core = { path = "../futures-core", version = "0.3.21", default-features = false }
+futures-sink = { path = "../futures-sink", version = "0.3.21", default-features = false, optional = true }
 
 [dev-dependencies]
 futures = { path = "../futures", default-features = true }