Bump github.com/docker/distribution in /img2lambda

Bumps [github.com/docker/distribution](https://github.com/docker/distribution) from 83389a148052d74ac602f5f1d62f86ff2f3c4aa5 to 2.7.1. This release includes the previously tagged commit.
- [Release notes](https://github.com/docker/distribution/releases)
- [Commits](distribution/distribution@83389a1...v2.7.1)

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

Author: dependabot-preview[bot]

img2lambda/Gopkg.lock

@@ -28,7 +28,7 @@
 
 [[override]]
   name = "github.com/docker/distribution"
-  revision = "83389a148052d74ac602f5f1d62f86ff2f3c4aa5"
+  version = "^2.7.1"
 
 [[constraint]]
   name = "gopkg.in/yaml.v2"