Bump github.com/containers/buildah from 1.21.0 to 1.21.1

Bumps [github.com/containers/buildah](https://github.com/containers/buildah) from 1.21.0 to 1.21.1.
- [Release notes](https://github.com/containers/buildah/releases)
- [Changelog](https://github.com/containers/buildah/blob/v1.21.1/CHANGELOG.md)
- [Commits](https://github.com/containers/buildah/compare/v1.21.0...v1.21.1)

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

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

vendor/github.com/containers/buildah/CHANGELOG.md

@@ -1,6 +1,9 @@
 ![buildah logo](https://cdn.rawgit.com/containers/buildah/master/logos/buildah-logo_large.png)
 
 # Changelog
+## v1.21.1 (2021-06-02)
+    Fix handling of auth.json file while in a user namespace
+
 ## v1.21.0 (2021-05-19)
     Don't blow up if cpp detects errors
     Vendor in containers/common v0.38.4

vendor/github.com/containers/buildah/changelog.txt

@@ -1,3 +1,6 @@
+- Changelog for v1.21.1 (2021-06-03)
+  * Fix handling of auth.json file while in a user namespace
+
 - Changelog for v1.21.0 (2021-05-19)
   * Don't blow up if cpp detects errors
   * Vendor in containers/common v0.38.4

vendor/github.com/containers/buildah/define/types.go

@@ -28,7 +28,7 @@ const (
 	Package = "buildah"
 	// Version for the Package.  Bump version in contrib/rpm/buildah.spec
 	// too.
-	Version = "1.21.0"
+	Version = "1.21.1"
 
 	// DefaultRuntime if containers.conf fails.
 	DefaultRuntime = "runc"