Bump github.com/docker/distribution

Bumps [github.com/docker/distribution](https://github.com/docker/distribution) from 2.7.1+incompatible to 2.8.0+incompatible.
- [Release notes](https://github.com/docker/distribution/releases)
- [Commits](https://github.com/docker/distribution/compare/v2.7.1...v2.8.0)

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

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

vendor/github.com/docker/distribution/registry/client/auth/challenge/authchallenge.go

@@ -117,8 +117,8 @@ func init() {
 		var t octetType
 		isCtl := c <= 31 || c == 127
 		isChar := 0 <= c && c <= 127
-		isSeparator := strings.IndexRune(" \t\"(),/:;<=>?@[]\\{}", rune(c)) >= 0
-		if strings.IndexRune(" \t\r\n", rune(c)) >= 0 {
+		isSeparator := strings.ContainsRune(" \t\"(),/:;<=>?@[]\\{}", rune(c))
+		if strings.ContainsRune(" \t\r\n", rune(c)) {
 			t |= isSpace
 		}
 		if isChar && !isCtl && !isSeparator {

vendor/github.com/docker/distribution/registry/client/repository.go

@@ -16,7 +16,7 @@ import (
 
 	"github.com/docker/distribution"
 	"github.com/docker/distribution/reference"
-	"github.com/docker/distribution/registry/api/v2"
+	v2 "github.com/docker/distribution/registry/api/v2"
 	"github.com/docker/distribution/registry/client/transport"
 	"github.com/docker/distribution/registry/storage/cache"
 	"github.com/docker/distribution/registry/storage/cache/memory"
@@ -736,7 +736,12 @@ func (bs *blobs) Create(ctx context.Context, options ...distribution.BlobCreateO
 		return nil, err
 	}
 
-	resp, err := bs.client.Post(u, "", nil)
+	req, err := http.NewRequest("POST", u, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	resp, err := bs.client.Do(req)
 	if err != nil {
 		return nil, err
 	}