Update img/media-types.dot

Co-authored-by: Brandon Mitchell <git@bmitch.net>
Signed-off-by: Sajay Antony <1821104+sajayantony@users.noreply.github.com>

Author: sajayantony

img/media-types.dot

@@ -18,5 +18,5 @@ digraph G {
   artifact -> artifact [label="0..1"];
   manifest -> manifest [label="0..1"];
   artifact -> imageIndex [label="1..1"]
-  artifact -> layer[label="1..*"]
+  artifact -> layer[label="0..*"]
 }