Fix first release date of Python 3.14

Author: m-aciek

include/release-cycle.json

@@ -13,7 +13,7 @@
     "pep": 745,
     "status": "prerelease",
     "beta_release": "2025-05-07",
-    "first_release": "2025-10-01",
+    "first_release": "2025-10-07",
     "end_of_life": "2030-10",
     "release_manager": "Hugo van Kemenade"
   },