ImageServlet: Suppress warning about deprecated Hashing.md5()

Change-Id: I6562bfd7ce55925892b0d126f02c06218d0d68c5
diff --git a/src/main/java/com/googlesource/gerrit/plugins/imagare/ImageServlet.java b/src/main/java/com/googlesource/gerrit/plugins/imagare/ImageServlet.java
index 768ca3e..8252fb2 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/imagare/ImageServlet.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/imagare/ImageServlet.java
@@ -208,6 +208,7 @@
     return path;
   }
 
+  @SuppressWarnings("deprecation")
   private static String computeETag(Project.NameKey project, ObjectId revId, String file) {
     return Hashing.md5()
         .newHasher()