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/redis.json

@@ -1,8 +1,5 @@
 {
   "releases": {
-    "8.0": {
-      "name": "8.0"
-    },
     "7.8": {
       "name": "7.8",
       "eol": "2027-05-30"
@@ -15,9 +12,6 @@
       "name": "7.2",
       "eol": "2026-02-28"
     },
-    "7.0": {
-      "name": "7.0"
-    },
     "6.4": {
       "name": "6.4",
       "eol": "2025-08-31"
@@ -41,9 +35,6 @@
     "5.2": {
       "name": "5.2",
       "eol": "2019-12-31"
-    },
-    "5.0": {
-      "name": "5.0"
     }
   },
   "versions": {