Cleanup leftover miniconda brew installation (pytorch#156898)

That results in torch.compile being unable to produce working artifacts

Should fix pytorch#156833

Pull Request resolved: pytorch#156898
Approved by: https://github.com/seemethere, https://github.com/atalman

Author: malfet

.github/workflows/_mac-test.yml

@@ -88,6 +88,10 @@ jobs:
             pkill "${PROCESS}" || true
           done
 
+      - name: Clean up leftover miniconda installation
+        continue-on-error: true
+        run: brew uninstall miniconda || true
+
       - name: Clean up leftover local python3 site-packages on MacOS pet runner
         continue-on-error: true
         run: |