Update pull-request.yml

Change python version for macos build from 3.8 to 3.9

Author: JustinWonjaePark

.github/workflows/pull-request.yml

@@ -35,7 +35,7 @@ jobs:
   build_macos:
     strategy:
       matrix:
-        python-version: [3.8, 3.11]
+        python-version: [3.9, 3.11]
     runs-on: macos-latest
     steps:
     - uses: actions/checkout@v3