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/ibm-aix.json

@@ -1,8 +1,5 @@
 {
   "releases": {
-    "7.3.3": {
-      "name": "7.3.3"
-    },
     "7.3.2": {
       "name": "7.3.2",
       "eol": "2026-11-30"
@@ -15,9 +12,6 @@
       "name": "7.3.0",
       "eol": "2024-12-31"
     },
-    "7.2.5": {
-      "name": "7.2.5"
-    },
     "7.2.4": {
       "name": "7.2.4",
       "eol": "2022-11-30"
@@ -41,9 +35,6 @@
     "7.1.5": {
       "name": "7.1.5",
       "eol": "2023-04-30"
-    },
-    "6.1.9": {
-      "name": "6.1.9"
     }
   },
   "versions": {