Use macos to install wxpython from pip instead of linux CI

Author: bobleesj

.github/workflows/tests-on-pr.yml

@@ -13,7 +13,7 @@ jobs:
       run:
         shell: bash -l {0}
 
-    runs-on: ubuntu-latest
+    runs-on: macos-latest
     steps:
       - name: Check out diffpy.labpdfproc repository
         uses: actions/checkout@v4