bump action versions to v3 (#140)

Author: jishnub

.github/workflows/downstream.yml

@@ -52,6 +52,6 @@ jobs:
             exit(0)  # Exit immediately, as a success
           end
       - uses: julia-actions/julia-processcoverage@v1
-      - uses: codecov/codecov-action@v2
+      - uses: codecov/codecov-action@v3
         with:
           files: lcov.info