Bump futures-util from 0.3.8 to 0.3.21

Bumps [futures-util](https://github.com/rust-lang/futures-rs) from 0.3.8 to 0.3.21.
- [Release notes](https://github.com/rust-lang/futures-rs/releases)
- [Changelog](https://github.com/rust-lang/futures-rs/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rust-lang/futures-rs/compare/0.3.8...0.3.21)

---
updated-dependencies:
- dependency-name: futures-util
  dependency-type: indirect
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Cargo.lock

@@ -1848,9 +1848,9 @@ dependencies = [
 
 [[package]]
 name = "futures-channel"
-version = "0.3.13"
+version = "0.3.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8c2dd2df839b57db9ab69c2c9d8f3e8c81984781937fe2807dc6dcf3b2ad2939"
+checksum = "c3083ce4b914124575708913bca19bfe887522d6e2e6d0952943f5eac4a74010"
 dependencies = [
  "futures-core",
  "futures-sink",
@@ -1858,9 +1858,9 @@ dependencies = [
 
 [[package]]
 name = "futures-core"
-version = "0.3.13"
+version = "0.3.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "15496a72fabf0e62bdc3df11a59a3787429221dd0710ba8ef163d6f7a9112c94"
+checksum = "0c09fd04b7e4073ac7156a9539b57a484a8ea920f79c7c675d05d289ab6110d3"
 
 [[package]]
 name = "futures-executor"
@@ -1875,17 +1875,16 @@ dependencies = [
 
 [[package]]
 name = "futures-io"
-version = "0.3.13"
+version = "0.3.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d71c2c65c57704c32f5241c1223167c2c3294fd34ac020c807ddbe6db287ba59"
+checksum = "fc4045962a5a5e935ee2fdedaa4e08284547402885ab326734432bed5d12966b"
 
 [[package]]
 name = "futures-macro"
-version = "0.3.8"
+version = "0.3.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "77408a692f1f97bcc61dc001d752e00643408fbc922e4d634c655df50d595556"
+checksum = "33c1e13800337f4d4d7a316bf45a567dbcb6ffe087f16424852d97e97a91f512"
 dependencies = [
- "proc-macro-hack",
  "proc-macro2",
  "quote",
  "syn",
@@ -1893,21 +1892,21 @@ dependencies = [
 
 [[package]]
 name = "futures-sink"
-version = "0.3.13"
+version = "0.3.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "85754d98985841b7d4f5e8e6fbfa4a4ac847916893ec511a2917ccd8525b8bb3"
+checksum = "21163e139fa306126e6eedaf49ecdb4588f939600f0b1e770f4205ee4b7fa868"
 
 [[package]]
 name = "futures-task"
-version = "0.3.13"
+version = "0.3.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fa189ef211c15ee602667a6fcfe1c1fd9e07d42250d2156382820fba33c9df80"
+checksum = "57c66a976bf5909d801bbef33416c41372779507e7a6b3a5e25e4749c58f776a"
 
 [[package]]
 name = "futures-util"
-version = "0.3.8"
+version = "0.3.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d304cff4a7b99cfb7986f7d43fbe93d175e72e704a8860787cc95e9ffd85cbd2"
+checksum = "d8b7abd5d659d9b90c8cba917f6ec750a74e2dc23902ef9cd4cc8c8b22e6036a"
 dependencies = [
  "futures 0.1.31",
  "futures-channel",
@@ -1917,10 +1916,8 @@ dependencies = [
  "futures-sink",
  "futures-task",
  "memchr",
- "pin-project 1.0.2",
+ "pin-project-lite 0.2.8",
  "pin-utils",
- "proc-macro-hack",
- "proc-macro-nested",
  "slab",
 ]
 
@@ -4752,12 +4749,6 @@ version = "0.5.19"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "dbf0c48bc1d91375ae5c3cd81e3722dff1abcf81a30960240640d223f59fe0e5"
 
-[[package]]
-name = "proc-macro-nested"
-version = "0.1.6"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "eba180dafb9038b050a4c280019bbedf9f2467b61e5d892dcad585bb57aadc5a"
-
 [[package]]
 name = "proc-macro2"
 version = "1.0.24"