Bump codecov/codecov-action from 5 to 6 (#3527)

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -41,7 +41,7 @@ jobs:
         env:
           JULIA_NUM_THREADS: 4,1
       - uses: julia-actions/julia-processcoverage@v1
-      - uses: codecov/codecov-action@v5
+      - uses: codecov/codecov-action@v6
         with:
           files: lcov.info
           token: ${{ secrets.CODECOV_TOKEN }}