bionic64.erb in boxes-3.6.0

- old
+ new

@@ -24,11 +24,11 @@
             <%- else -%>
             "guest_os_type": "Ubuntu_64",
             <%- end -%>
             "headless": true,
 
-            "iso_url": "http://cdimage.ubuntu.com/releases/18.04/release/ubuntu-18.04.2-server-amd64.iso",
-            "iso_checksum": "a2cb36dc010d98ad9253ea5ad5a07fd6b409e3412c48f1860536970b073c98f5",
+            "iso_url": "http://cdimage.ubuntu.com/ubuntu/releases/18.04/release/ubuntu-18.04.4-server-amd64.iso",
+            "iso_checksum": "e2ecdace33c939527cbc9e8d23576381c493b071107207d2040af72595f8990b",
             "iso_checksum_type": "sha256",
 
             "ssh_username": "vagrant",
             "ssh_password": "vagrant",
             "ssh_timeout": "15m",