build(deps): bump github.com/moby/buildkit from 0.9.2 to 0.9.3

Bumps [github.com/moby/buildkit](https://github.com/moby/buildkit) from 0.9.2 to 0.9.3.
- [Release notes](https://github.com/moby/buildkit/releases)
- [Commits](https://github.com/moby/buildkit/compare/v0.9.2...v0.9.3)

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

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

go.mod

@@ -8,7 +8,7 @@ require (
 	github.com/KromDaniel/jonson v0.0.0-20180630143114-d2f9c3c389db
 	github.com/Microsoft/go-winio v0.5.1
 	github.com/containerd/console v1.0.3
-	github.com/containerd/containerd v1.5.7
+	github.com/containerd/containerd v1.5.8
 	github.com/docker/buildx v0.6.2
 	github.com/docker/distribution v2.7.1+incompatible
 	github.com/emicklei/proto v1.9.0 // indirect
@@ -20,7 +20,7 @@ require (
 	github.com/mattn/go-colorable v0.1.8 // indirect
 	github.com/mitchellh/colorstring v0.0.0-20190213212951-d06e56a500db
 	github.com/mitchellh/go-homedir v1.1.0
-	github.com/moby/buildkit v0.9.2
+	github.com/moby/buildkit v0.9.3
 	github.com/morikuni/aec v1.0.0
 	github.com/opencontainers/go-digest v1.0.0
 	github.com/opencontainers/image-spec v1.0.1