Merge pull request #107 from nextstrain/remove-ubuntu-20.04

.github/workflows/installation: Update ubuntu runners

Author: joverlee521

.github/workflows/installation.yaml

@@ -25,8 +25,8 @@ jobs:
       fail-fast: false
       matrix:
         os:
-          - ubuntu-20.04
           - ubuntu-22.04
+          - ubuntu-24.04
           - macos-13
           - macos-14
           - macos-15