Bumped github ubuntu workflow: Arduino-CI/[email protected] -> Arduino-CI/[email protected] (#11)

Thanks!

Author: s-t-a-n

.github/workflows/ubuntu.yaml

@@ -9,4 +9,4 @@ jobs:
 
     steps:
       - uses: actions/checkout@v2
-      - uses: Arduino-CI/action@v0.1.0
+      - uses: Arduino-CI/action@stable-1.x