Try self-hosted runner yet another time

.github/workflows/osrm-backend.yml

@@ -727,6 +727,8 @@ jobs:
       # we run benchmarks in tmpfs to avoid impact of disk IO
       - name: Create folder for tmpfs 
         run: |
+          # if by any chance it was mounted before(e.g. due to previous job failed), unmount it
+          sudo umount ~/benchmarks | true
           rm -rf ~/benchmarks 
           mkdir -p ~/benchmarks
       - name: Run PR Benchmarks