Use modern action version in sketch compilation workflow

The GitHub Actions action used to do a "smoke test" compilation of the examples has graduated from an "experimental"
project to a stable state and been moved from its original home in the `arduino/actions` repository to a dedicated
permanent home at `arduino/compile-sketches`. The copy in the previous repository is unmaintained and deprecated and its
use results in a warning of such in the workflow run summary and logs.

Author: per1234

.github/workflows/compile-examples.yml

@@ -199,7 +199,7 @@ jobs:
         uses: actions/checkout@v2
 
       - name: Compile examples
-        uses: arduino/actions/libraries/compile-examples@master
+        uses: arduino/compile-sketches@v1
         with:
           fqbn: ${{ matrix.board.fqbn }}
           libraries: |