update drone.yml to set registry

.drone.yml

@@ -1,6 +1,10 @@
 pipeline:
   build:
     image: registry.nadal-fr.com:443/buildroot_dev
-    secrets: [ registry_username, registry_password ]
+    environment:
+      USERNAME:
+        from_secret: registry_username
+      PASSWORD:
+        from_secret: registry_password
     commands:
       - make -C projects/rpi_domo/ buildroot.check-package