Use existing key

Co-authored-by: Charles de Beauchesne <charles.debeauchesne@datadoghq.com>

Author: nccatoni

.github/workflows/dev.yml

@@ -186,7 +186,7 @@ jobs:
     needs: build-system-tests-artifact
     uses: DataDog/system-tests/.github/workflows/system-tests.yml@main
     secrets:
-      TEST_OPTIMIZATION_API_KEY: ${{ secrets.DD_API_KEY }}
+      TEST_OPTIMIZATION_API_KEY: ${{ secrets.DD_CI_VIS_API_KEY }}
     permissions:
       contents: read
       packages: write