Updated CI releases inventory after 8.15.2 (#16474)

Author: andsel

ci/logstash_releases.json

@@ -3,11 +3,11 @@
     "5.x": "5.6.16",
     "6.x": "6.8.23",
     "7.x": "7.17.24",
-    "8.x": "8.15.1"
+    "8.x": "8.15.2"
   },
   "snapshots": {
     "7.x": "7.17.25-SNAPSHOT",
-    "8.15": "8.15.2-SNAPSHOT",
+    "8.15": "8.15.3-SNAPSHOT",
     "8.x": "8.16.0-SNAPSHOT",
     "main": "9.0.0-SNAPSHOT"
   }