Set CODECOV_TOKEN to upload results from the upstream branches (#3165)

https://kubernetes.slack.com/archives/C047LA9MUPJ/p1708300085013439

Signed-off-by: shuheiktgw <s-kitagawa@mercari.com>

.github/workflows/ci.yml

@@ -127,6 +127,8 @@ jobs:
 
       - name: Publish Unit Test Coverage
         uses: codecov/codecov-action@e0b68c6749509c5f83f984dd99a76a1c1a231044 # v4.0.1
+        env:
+          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
         with:
           flags: unittests
           file: ./cover.out