Add PyPy 7.3.21

<https://pypy.org/posts/2026/03/pypy-v7320-release.html>

Author: jwodder

pyversion-info-data.v1.json

@@ -1,5 +1,5 @@
 {
-    "last_modified": "2026-03-03T20:37:26+00:00",
+    "last_modified": "2026-03-13T15:16:29+00:00",
     "cpython": {
         "release_dates": {
             "0.9.0": "1991-02-20",
@@ -395,7 +395,8 @@
             "7.3.17": "2024-08-28",
             "7.3.18": "2025-02-06",
             "7.3.19": "2025-02-26",
-            "7.3.20": "2025-07-04"
+            "7.3.20": "2025-07-04",
+            "7.3.21": "2026-03-13"
         },
         "cpython_versions": {
             "1.6.0": [
@@ -630,6 +631,10 @@
             "7.3.20": [
                 "2.7.18",
                 "3.11.13"
+            ],
+            "7.3.21": [
+                "2.7.18",
+                "3.11.15"
             ]
         }
     }