Revert "Fix build (again!)"

This reverts commit 8bf69df.

Author: sol

.github/workflows/build.yml

@@ -22,7 +22,7 @@ jobs:
     strategy:
       matrix:
         os:
-          - ubuntu-20.04
+          - ubuntu-latest
         ghc:
           - '8.2'
           - '8.4'