ci(oetf-kind): revert diagnostic testlog-upload to failure-only

The label scenario is green (Ran 6 tests, OK); restore the upload step's
if: failure() guard now that the diagnostic served its purpose.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: jiaenren

.github/workflows/oetf-kind.yaml

@@ -301,7 +301,7 @@ jobs:
           if-no-files-found: warn
 
       - name: Upload bazel test logs
-        if: always()
+        if: failure()
         uses: actions/upload-artifact@4cec3d8aa04e39d1a68397de0c4cd6fb9dce8ec1 # v4.6.1
         with:
           name: bazel-testlogs