Discard unneeded output from asv machine step.

Configuring a machine name that doesn't match the current hostname
outputs an unneeded warning.

.github/workflows/benchmark.yml

@@ -24,7 +24,7 @@ jobs:
       - name: Run Benchmarks
         shell: bash -l {0}
         run: |-
-          asv machine --machine ubuntu-latest --yes
+          asv machine --machine ubuntu-latest --yes > /dev/null
           echo '```' >> $GITHUB_STEP_SUMMARY
           asv continuous --interleave-processes -a processes=2 --split --show-stderr 'HEAD^' 'HEAD' |\
           sed -n -E '/(before.*after.*ratio)|(BENCHMARKS)/,$p' >> out.txt