fix: remove CODECOV_TOKEN for tokenless public repo upload

Codecov upload was failing with 404 'Repository not found' because
the token secret was empty. Public repos support tokenless uploads.

Author: kolkov

.github/workflows/ci.yml

@@ -144,7 +144,6 @@ jobs:
         if: matrix.os == 'ubuntu-latest'
         uses: codecov/codecov-action@v5
         with:
-          token: ${{ secrets.CODECOV_TOKEN }}
           slug: go-webgpu/goffi
           files: ./coverage.txt
           flags: unittests