Fix missing eol field in unstable 3.3 versions

Author: marc1706

phpbb/versions.json

@@ -48,6 +48,7 @@
         "3.3": {
             "current": "3.3.19",
             "announcement": "https://www.phpbb.com/community/viewtopic.php?t=2675305",
+            "eol": null,
             "security": "3.3.19",
             "urgent": "3.3.19"
         },