Fix CI runner version

Author: javieraspuru-ax

.fernignore

@@ -4,4 +4,5 @@ src/axiomatic/client.py
 src/axiomatic/document_helpers.py
 src/axiomatic/magic.py
 src/axiomatic/pic_helpers.py
-src/axiomatic/axtract/
+src/axiomatic/axtract/
+.github/workflows/ci.yml

.github/workflows/ci.yml

@@ -3,7 +3,7 @@ name: ci
 on: [push]
 jobs:
   compile:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     steps:
       - name: Checkout repo
         uses: actions/checkout@v3