Change container source for docker-tests

Signed-off-by: Federico Guerinoni <guerra@develer.com>

Author: Federico Guerinoni

.github/workflows/tests.yml

@@ -6,7 +6,7 @@ jobs:
   docker-tests:
     name: docker-tests
     runs-on: ubuntu-latest
-    container: guerra1994/go-mqtt-docker-env
+    container: docker.pkg.github.com/arduino/go-mqtt-docker-env/go-mqtt-docker-env:latest
 
     steps:
       - name: check out code