Extend script to unassign inactive people to bugs with last activity within the previous 6 months (#1297)

Part of #266

Co-authored-by: calixteman <calixte.denizet@gmail.com>

auto_nag/scripts/configs/tools.json

@@ -186,7 +186,7 @@
     "assignee_no_login":
     {
         "number_of_months": 7,
-        "last_activity_months": 3,
+        "last_activity_months": 6,
         "receivers":
         [
             "calixte@mozilla.com",