Bump mpdecimal from 2.5.1 to 4.0.0 (#353)

Author: zanieb

pythonbuild/downloads.py

@@ -212,10 +212,10 @@
         "version": "1.4.19",
     },
     "mpdecimal": {
-        "url": "https://www.bytereef.org/software/mpdecimal/releases/mpdecimal-2.5.1.tar.gz",
-        "size": 2584021,
-        "sha256": "9f9cd4c041f99b5c49ffb7b59d9f12d95b683d88585608aa56a6307667b2b21f",
-        "version": "2.5.1",
+        "url": "https://www.bytereef.org/software/mpdecimal/releases/mpdecimal-4.0.0.tar.gz",
+        "size": 315325,
+        "sha256": "942445c3245b22730fd41a67a7c5c231d11cb1b9936b9c0f76334fb7d0b4468c",
+        "version": "4.0.0",
         "library_names": ["mpdec"],
         "licenses": ["BSD-2-Clause"],
         "license_file": "LICENSE.mpdecimal.txt",