Update to Jenkins 2.73.1

It should notably fix the root cause of #86.

Change-Id: If671d5d24169d2930cf2bbe1f085dda8e02364ec
diff --git a/WORKSPACE b/WORKSPACE
index eb55e48..53f35cb 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -40,8 +40,8 @@
 jenkins_base(
     name = "jenkins",
     plugins = JENKINS_PLUGINS,
-    version = "2.60.2",
-    digest = "sha256:2686bba435a53d8bff0cb5380a341cbf2a337ce789db4753f30367f38a3239e6",
+    version = "2.73.1",
+    digest = "sha256:deb7144257b8f332cd4a036ea14d7c27ee7cb1b79063170a6cdf3929269cd9dc",
     volumes = ["/opt/secrets"],
 )