Update belgium.json

https://www.ibpt.be/consommateurs/publication/decision-du-29-aout-2023-concernant-l-attribution-du-spectre-40.660-mhz---40.690-mhz-a-des-stations-de-radiocommunications-privees-dinstruction-individuelle-dintercommunication-technique-et-detudes-utilisees-par-des-radioamateurs

root/res/bandplans/belgium.json

@@ -149,6 +149,12 @@
       "start": 28000000,
       "end": 29700000
     },
+    {
+      "name": "8m - Amateur",
+      "type": "amateur",
+      "start": 40660000,
+      "end": 40690000
+    },
     {
       "name": "6m - Amateur",
       "type": "amateur",