Bump futures from 0.3.17 to 0.3.21

Bumps [futures](https://github.com/rust-lang/futures-rs) from 0.3.17 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/0.3.17...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>

Cargo.lock

@@ -1141,9 +1141,9 @@ checksum = "a06f77d526c1a601b7c4cdd98f54b5eaabffc14d5f2f0296febdc7f357c6d3ba"
 
 [[package]]
 name = "futures"
-version = "0.3.17"
+version = "0.3.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a12aa0eb539080d55c3f2d45a67c3b58b6b0773c1a3ca2dfec66d58c97fd66ca"
+checksum = "f73fe65f54d1e12b726f517d3e2135ca3125a437b6d998caf1962961f7172d9e"
 dependencies = [
  "futures-channel",
  "futures-core",
@@ -1156,9 +1156,9 @@ dependencies = [
 
 [[package]]
 name = "futures-channel"
-version = "0.3.17"
+version = "0.3.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5da6ba8c3bb3c165d3c7319fc1cc8304facf1fb8db99c5de877183c08a273888"
+checksum = "c3083ce4b914124575708913bca19bfe887522d6e2e6d0952943f5eac4a74010"
 dependencies = [
  "futures-core",
  "futures-sink",
@@ -1166,15 +1166,15 @@ dependencies = [
 
 [[package]]
 name = "futures-core"
-version = "0.3.17"
+version = "0.3.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "88d1c26957f23603395cd326b0ffe64124b818f4449552f960d815cfba83a53d"
+checksum = "0c09fd04b7e4073ac7156a9539b57a484a8ea920f79c7c675d05d289ab6110d3"
 
 [[package]]
 name = "futures-executor"
-version = "0.3.17"
+version = "0.3.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "45025be030969d763025784f7f355043dc6bc74093e4ecc5000ca4dc50d8745c"
+checksum = "9420b90cfa29e327d0429f19be13e7ddb68fa1cccb09d65e5706b8c7a749b8a6"
 dependencies = [
  "futures-core",
  "futures-task",
@@ -1195,18 +1195,16 @@ dependencies = [
 
 [[package]]
 name = "futures-io"
-version = "0.3.17"
+version = "0.3.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "522de2a0fe3e380f1bc577ba0474108faf3f6b18321dbf60b3b9c39a75073377"
+checksum = "fc4045962a5a5e935ee2fdedaa4e08284547402885ab326734432bed5d12966b"
 
 [[package]]
 name = "futures-macro"
-version = "0.3.17"
+version = "0.3.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "18e4a4b95cea4b4ccbcf1c5675ca7c4ee4e9e75eb79944d07defde18068f79bb"
+checksum = "33c1e13800337f4d4d7a316bf45a567dbcb6ffe087f16424852d97e97a91f512"
 dependencies = [
- "autocfg 1.0.1",
- "proc-macro-hack",
  "proc-macro2",
  "quote",
  "syn",
@@ -1225,15 +1223,15 @@ dependencies = [
 
 [[package]]
 name = "futures-sink"
-version = "0.3.17"
+version = "0.3.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "36ea153c13024fe480590b3e3d4cad89a0cfacecc24577b68f86c6ced9c2bc11"
+checksum = "21163e139fa306126e6eedaf49ecdb4588f939600f0b1e770f4205ee4b7fa868"
 
 [[package]]
 name = "futures-task"
-version = "0.3.17"
+version = "0.3.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1d3d00f4eddb73e498a54394f228cd55853bdf059259e8e7bc6e69d408892e99"
+checksum = "57c66a976bf5909d801bbef33416c41372779507e7a6b3a5e25e4749c58f776a"
 
 [[package]]
 name = "futures-timer"
@@ -1243,11 +1241,10 @@ checksum = "e64b03909df88034c26dc1547e8970b91f98bdb65165d6a4e9110d94263dbb2c"
 
 [[package]]
 name = "futures-util"
-version = "0.3.17"
+version = "0.3.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "36568465210a3a6ee45e1f165136d68671471a501e632e9a98d96872222b5481"
+checksum = "d8b7abd5d659d9b90c8cba917f6ec750a74e2dc23902ef9cd4cc8c8b22e6036a"
 dependencies = [
- "autocfg 1.0.1",
  "futures-channel",
  "futures-core",
  "futures-io",
@@ -1257,8 +1254,6 @@ dependencies = [
  "memchr",
  "pin-project-lite 0.2.8",
  "pin-utils",
- "proc-macro-hack",
- "proc-macro-nested",
  "slab",
 ]
 
@@ -2777,18 +2772,6 @@ dependencies = [
  "version_check",
 ]
 
-[[package]]
-name = "proc-macro-hack"
-version = "0.5.19"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dbf0c48bc1d91375ae5c3cd81e3722dff1abcf81a30960240640d223f59fe0e5"
-
-[[package]]
-name = "proc-macro-nested"
-version = "0.1.7"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bc881b2c22681370c6a780e47af9840ef841837bc98118431d4e1868bd0c1086"
-
 [[package]]
 name = "proc-macro2"
 version = "1.0.27"