v3 of checkout action

Author: jecisc

.github/workflows/continuous.yml

@@ -12,7 +12,7 @@ jobs:
         smalltalk: [ Pharo64-9.0, Pharo64-10, Pharo64-11 ]
     name: ${{ matrix.smalltalk }}
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - uses: hpi-swa/setup-smalltalkCI@v1
         with:
           smalltalk-image: ${{ matrix.smalltalk }}