CI: Switch to ubuntu-latest

Author: mmicko

.github/workflows/ci.yml

@@ -3,7 +3,7 @@ on: [push, pull_request]
 
 jobs:
   test:
-    runs-on: ubuntu-20.04 # Ubuntu 20.04 LTS ships with the Python version we're currently targeting
+    runs-on: ubuntu-latest
 
     steps:
       - uses: actions/checkout@v4
@@ -18,7 +18,7 @@ jobs:
           python .github/workflows/get_markdown.py .coverage.xml 90
 
   check:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
 
     steps:
       - uses: actions/checkout@v4