Bump github.com/docker/docker

Bumps [github.com/docker/docker](https://github.com/docker/docker) from 20.10.20+incompatible to 20.10.21+incompatible.
- [Release notes](https://github.com/docker/docker/releases)
- [Changelog](https://github.com/moby/moby/blob/master/CHANGELOG.md)
- [Commits](moby/moby@v20.10.20...v20.10.21)

---
updated-dependencies:
- dependency-name: github.com/docker/docker
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

go.mod

@@ -17,7 +17,7 @@ require (
 	github.com/cenkalti/backoff/v4 v4.1.3
 	github.com/cheggaaa/pb/v3 v3.1.0
 	github.com/cloudevents/sdk-go/v2 v2.12.0
-	github.com/docker/docker v20.10.20+incompatible
+	github.com/docker/docker v20.10.21+incompatible
 	github.com/docker/go-units v0.5.0
 	github.com/docker/machine v0.16.2
 	github.com/elazarl/goproxy v0.0.0-20210110162100-a92cc753f88e

go.sum

@@ -365,8 +365,8 @@ github.com/docker/distribution v2.8.1+incompatible h1:Q50tZOPR6T/hjNsyc9g8/syEs6
 github.com/docker/distribution v2.8.1+incompatible/go.mod h1:J2gT2udsDAN96Uj4KfcMRqY0/ypR+oyYUYmja8H+y+w=
 github.com/docker/docker v17.12.0-ce-rc1.0.20181225093023-5ddb1d410a8b+incompatible/go.mod h1:eEKB0N0r5NX/I1kEveEz05bcu8tLC/8azJZsviup8Sk=
 github.com/docker/docker v17.12.0-ce-rc1.0.20190115220918-5ec31380a5d3+incompatible/go.mod h1:eEKB0N0r5NX/I1kEveEz05bcu8tLC/8azJZsviup8Sk=
-github.com/docker/docker v20.10.20+incompatible h1:kH9tx6XO+359d+iAkumyKDc5Q1kOwPuAUaeri48nD6E=
-github.com/docker/docker v20.10.20+incompatible/go.mod h1:eEKB0N0r5NX/I1kEveEz05bcu8tLC/8azJZsviup8Sk=
+github.com/docker/docker v20.10.21+incompatible h1:UTLdBmHk3bEY+w8qeO5KttOhy6OmXWsl/FEet9Uswog=
+github.com/docker/docker v20.10.21+incompatible/go.mod h1:eEKB0N0r5NX/I1kEveEz05bcu8tLC/8azJZsviup8Sk=
 github.com/docker/docker-credential-helpers v0.7.0 h1:xtCHsjxogADNZcdv1pKUHXryefjlVRqWqIhk/uXJp0A=
 github.com/docker/docker-credential-helpers v0.7.0/go.mod h1:rETQfLdHNT3foU5kuNkFR1R1V12OJRRO5lzt2D1b5X0=
 github.com/docker/go-connections v0.4.0 h1:El9xVISelRB7BuFusrZozjnkIM5YnzCViNKohAFqRJQ=