Update vendor dependencies

Signed-off-by: Emile Vauge <emile@vauge.com>

vendor/github.com/docker/distribution/context/util.go

@@ -1,24 +0,0 @@
-package context
-
-import (
-	"time"
-)
-
-// Since looks up key, which should be a time.Time, and returns the duration
-// since that time. If the key is not found, the value returned will be zero.
-// This is helpful when inferring metrics related to context execution times.
-func Since(ctx Context, key interface{}) time.Duration {
-	if startedAt, ok := ctx.Value(key).(time.Time); ok {
-		return time.Since(startedAt)
-	}
-	return 0
-}
-
-// GetStringValue returns a string value from the context. The empty string
-// will be returned if not found.
-func GetStringValue(ctx Context, key interface{}) (value string) {
-	if valuev, ok := ctx.Value(key).(string); ok {
-		value = valuev
-	}
-	return value
-}