Update test to use node 17 PR

Author: lloeki

.github/workflows/build.yml

@@ -395,7 +395,7 @@ jobs:
         run: |
           git clone https://github.com/rubyjs/mini_racer.git test/mini_racer --depth 1
           cd test/mini_racer
-          git fetch origin refs/pull/210/head
+          git fetch origin refs/pull/231/head
           git checkout FETCH_HEAD
           git reset --hard
           git clean -f -d -x