Deduplicate MD4 and MD5 entries in cryptography registry (#879)

Removes duplicate `MD4` and `MD5` family entries from the cryptography
registry.

Fixes #878

Author: stevespringett

schema/cryptography-defs.json

@@ -601,36 +601,6 @@
         }
       ]
     },
-    {
-      "family": "MD5",
-      "standard": [
-        {
-          "name": "RFC1321",
-          "url": "https://doi.org/10.17487/RFC1321"
-        }
-      ],
-      "variant": [
-        {
-          "pattern": "MD5",
-          "primitive": "hash"
-        }
-      ]
-    },
-    {
-      "family": "MD4",
-      "standard": [
-        {
-          "name": "RFC1320",
-          "url": "https://doi.org/10.17487/RFC1320"
-        }
-      ],
-      "variant": [
-        {
-          "pattern": "MD4",
-          "primitive": "hash"
-        }
-      ]
-    },
     {
       "family": "RC4",
       "standard": [