Remove invalid releases automatically (#466)

Automatically remove empty releases or releases which are released in the future, regardless of the product.

Also refactored a bit releasedata.py to use better names and clarify types.

releases/nexus.json

@@ -173,9 +173,6 @@
       "eoas": "2024-05-22",
       "eol": "2024-11-22"
     },
-    "3.53": {
-      "name": "3.53"
-    },
     "3.52": {
       "name": "3.52",
       "releaseDate": "2023-04-18",
@@ -310,9 +307,6 @@
       "name": "3.29",
       "releaseDate": "2020-12-04",
       "eol": "2022-06-04"
-    },
-    "2": {
-      "name": "2"
     }
   },
   "versions": {