Update c/image from the main branch

> go get github.com/containers/image/v5@main
> make vendor

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

vendor/google.golang.org/grpc/metadata/metadata.go

@@ -91,7 +91,11 @@ func (md MD) Len() int {
 
 // Copy returns a copy of md.
 func (md MD) Copy() MD {
-	return Join(md)
+	out := make(MD, len(md))
+	for k, v := range md {
+		out[k] = copyOf(v)
+	}
+	return out
 }
 
 // Get obtains the values for a given key.
@@ -171,8 +175,11 @@ func AppendToOutgoingContext(ctx context.Context, kv ...string) context.Context
 	md, _ := ctx.Value(mdOutgoingKey{}).(rawMD)
 	added := make([][]string, len(md.added)+1)
 	copy(added, md.added)
-	added[len(added)-1] = make([]string, len(kv))
-	copy(added[len(added)-1], kv)
+	kvCopy := make([]string, 0, len(kv))
+	for i := 0; i < len(kv); i += 2 {
+		kvCopy = append(kvCopy, strings.ToLower(kv[i]), kv[i+1])
+	}
+	added[len(added)-1] = kvCopy
 	return context.WithValue(ctx, mdOutgoingKey{}, rawMD{md: md.md, added: added})
 }