Merge pull request #1928 from timmaffett/fix_action_rmi_error

Update main.yml to correct docker rmi command. Fixes #1927
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index ce803c8..6538120 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -15,7 +15,7 @@
         sudo swapoff -a
         sudo rm -f /swapfile
         sudo apt clean
-        docker rmi $(docker image ls -aq)
+        docker image prune -a -f
         df -h
     - uses: actions/checkout@v3
     - name: Set up Python