build(ci): Fix artifact handling in Conbench Upload job (facebookincubator#12183)

Summary:
The v4 artifact action handles paths different leading to the 'benchmark-results' dir getting dropped.

Working run of the fixed workflow: https://github.com/facebookincubator/velox/actions/runs/12994805091/job/36240073932#step:8:26

Pull Request resolved: facebookincubator#12183

Reviewed By: kagamiori

Differential Revision: D68721703

Pulled By: kgpai

fbshipit-source-id: b2f9f852d153442f94d89c6da5cc1cdfea126f5c

Author: assignUser

.github/workflows/conbench_upload.yml

@@ -108,7 +108,7 @@ jobs:
           --run_id "GHA-${{ github.run_id }}-${{ github.run_attempt }}" \
           --pr_number "${{ steps.extract.outputs.pr_number }}" \
           --sha "${{ steps.download.outputs.contender_sha }}" \
-          --output_dir "/tmp/artifacts/benchmark-results/contender/"
+          --output_dir "/tmp/artifacts/contender/"
 
     - name: "Check the status of the upload"
       # Status functions like failure() only work in `if:`