gha: configure codecov slug properly

Our main branch has been failing to upload coverage to CodeCov for a
month with the following error:

  error - 2025-11-11 05:32:32,830 -- Upload failed: {"message":"Repository not found"}

Hopefully configuring the slug explicitly will resolve this issue...

Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>

Author: cyphar

.github/workflows/ci.yml

@@ -86,11 +86,10 @@ jobs:
       - run: go tool covdata textfmt -i "$GOCOVERDIR" -o "$COVERAGE"
       - name: codecov
         uses: codecov/codecov-action@v5
-        env:
-          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
         with:
+          token: ${{ secrets.CODECOV_TOKEN }}
+          slug: opencontainers/umoci
           files: ${{ env.COVERAGE }}
-          flags: unit,macos
       - name: upload coverage
         uses: actions/upload-artifact@v5
         with:
@@ -122,11 +121,10 @@ jobs:
       - run: go tool covdata textfmt -i "$GOCOVERDIR" -o "$COVERAGE"
       - name: codecov
         uses: codecov/codecov-action@v5
-        env:
-          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
         with:
+          token: ${{ secrets.CODECOV_TOKEN }}
+          slug: opencontainers/umoci
           files: ${{ env.COVERAGE }}
-          flags: unit,linux
       - name: upload coverage
         uses: actions/upload-artifact@v5
         with:
@@ -172,11 +170,10 @@ jobs:
       - run: go tool covdata textfmt -i "$GOCOVERDIR" -o "$COVERAGE"
       - name: codecov
         uses: codecov/codecov-action@v5
-        env:
-          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
         with:
+          token: ${{ secrets.CODECOV_TOKEN }}
+          slug: opencontainers/umoci
           files: ${{ env.COVERAGE }}
-          flags: integration,linux
       - name: upload coverage
         uses: actions/upload-artifact@v5
         with: