build(deps): bump futures from 0.3.19 to 0.3.21 (#1468)

Bumps [futures](https://github.com/rust-lang/futures-rs) from 0.3.19 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](rust-lang/futures-rs@0.3.19...0.3.21)

---
updated-dependencies:
- dependency-name: futures
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Cargo.lock

@@ -341,9 +341,9 @@ checksum = "2022715d62ab30faffd124d40b76f4134a550a87792276512b18d63272333394"
 
 [[package]]
 name = "futures"
-version = "0.3.19"
+version = "0.3.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "28560757fe2bb34e79f907794bb6b22ae8b0e5c669b638a1132f2592b19035b4"
+checksum = "f73fe65f54d1e12b726f517d3e2135ca3125a437b6d998caf1962961f7172d9e"
 dependencies = [
  "futures-channel",
  "futures-core",
@@ -356,25 +356,25 @@ dependencies = [
 
 [[package]]
 name = "futures-channel"
-version = "0.3.19"
+version = "0.3.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ba3dda0b6588335f360afc675d0564c17a77a2bda81ca178a4b6081bd86c7f0b"
+checksum = "c3083ce4b914124575708913bca19bfe887522d6e2e6d0952943f5eac4a74010"
 dependencies = [
  "futures-core",
  "futures-sink",
 ]
 
 [[package]]
 name = "futures-core"
-version = "0.3.19"
+version = "0.3.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d0c8ff0461b82559810cdccfde3215c3f373807f5e5232b71479bff7bb2583d7"
+checksum = "0c09fd04b7e4073ac7156a9539b57a484a8ea920f79c7c675d05d289ab6110d3"
 
 [[package]]
 name = "futures-executor"
-version = "0.3.19"
+version = "0.3.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "29d6d2ff5bb10fb95c85b8ce46538a2e5f5e7fdc755623a7d4529ab8a4ed9d2a"
+checksum = "9420b90cfa29e327d0429f19be13e7ddb68fa1cccb09d65e5706b8c7a749b8a6"
 dependencies = [
  "futures-core",
  "futures-task",
@@ -383,27 +383,27 @@ dependencies = [
 
 [[package]]
 name = "futures-io"
-version = "0.3.19"
+version = "0.3.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b1f9d34af5a1aac6fb380f735fe510746c38067c5bf16c7fd250280503c971b2"
+checksum = "fc4045962a5a5e935ee2fdedaa4e08284547402885ab326734432bed5d12966b"
 
 [[package]]
 name = "futures-sink"
-version = "0.3.19"
+version = "0.3.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e3055baccb68d74ff6480350f8d6eb8fcfa3aa11bdc1a1ae3afdd0514617d508"
+checksum = "21163e139fa306126e6eedaf49ecdb4588f939600f0b1e770f4205ee4b7fa868"
 
 [[package]]
 name = "futures-task"
-version = "0.3.19"
+version = "0.3.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6ee7c6485c30167ce4dfb83ac568a849fe53274c831081476ee13e0dce1aad72"
+checksum = "57c66a976bf5909d801bbef33416c41372779507e7a6b3a5e25e4749c58f776a"
 
 [[package]]
 name = "futures-util"
-version = "0.3.19"
+version = "0.3.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d9b5cf40b47a271f77a8b1bec03ca09044d99d2372c0de244e66430761127164"
+checksum = "d8b7abd5d659d9b90c8cba917f6ec750a74e2dc23902ef9cd4cc8c8b22e6036a"
 dependencies = [
  "futures-channel",
  "futures-core",