Downgrade codecov action to v3 (#337)

Author: jishnub

.github/workflows/ci.yml

@@ -64,6 +64,6 @@ jobs:
       - uses: julia-actions/julia-buildpkg@v1
       - uses: julia-actions/julia-runtest@v1
       - uses: julia-actions/julia-processcoverage@v1
-      - uses: codecov/codecov-action@v4
+      - uses: codecov/codecov-action@v3
         with:
           file: lcov.info

.github/workflows/downstream.yml

@@ -71,6 +71,6 @@ jobs:
             exit(0)  # Exit immediately, as a success
           end
       - uses: julia-actions/julia-processcoverage@v1
-      - uses: codecov/codecov-action@v4
+      - uses: codecov/codecov-action@v3
         with:
           files: lcov.info