Renovate: actions/upload-artifact to b4b15b8 (#425)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/paper.yaml

@@ -23,7 +23,7 @@ jobs:
 
       - name: Upload
         # yamllint disable-line rule:line-length
-        uses: actions/upload-artifact@834a144ee995460fba8ed112a2fc961b36a5ec5a # v4
+        uses: actions/upload-artifact@b4b15b8c7c6ac21ea08fcf65892d2ee8f75cf882 # v4
         with:
           name: paper
           path: paper/paper.pdf