build(deps): 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
...

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

vendor/github.com/docker/distribution/vendor.conf

@@ -8,7 +8,7 @@ github.com/bugsnag/bugsnag-go b1d153021fcd90ca3f080db36bec96dc690fb274
 github.com/bugsnag/osext 0dd3f918b21bec95ace9dc86c7e70266cfc5c702
 github.com/bugsnag/panicwrap e2c28503fcd0675329da73bf48b33404db873782
 github.com/denverdino/aliyungo afedced274aa9a7fcdd47ac97018f0f8db4e5de2
-github.com/dgrijalva/jwt-go a601269ab70c205d26370c16f7c81e9017c14e04
+github.com/dgrijalva/jwt-go 4bbdd8ac624fc7a9ef7aec841c43d99b5fe65a29 https://github.com/golang-jwt/jwt.git # v3.2.2
 github.com/docker/go-metrics 399ea8c73916000c64c2c76e8da00ca82f8387ab
 github.com/docker/libtrust fa567046d9b14f6aa788882a950d69651d230b21
 github.com/garyburd/redigo 535138d7bcd717d6531c701ef5933d98b1866257
@@ -48,4 +48,4 @@ gopkg.in/square/go-jose.v1 40d457b439244b546f023d056628e5184136899b
 gopkg.in/yaml.v2 v2.2.1
 rsc.io/letsencrypt e770c10b0f1a64775ae91d240407ce00d1a5bdeb https://github.com/dmcgowan/letsencrypt.git
 github.com/opencontainers/go-digest a6d0ee40d4207ea02364bd3b9e8e77b9159ba1eb
-github.com/opencontainers/image-spec ab7389ef9f50030c9b245bc16b981c7ddf192882
+github.com/opencontainers/image-spec 67d2d5658fe0476ab9bf414cec164077ebff3920 # v1.0.2