CI: use latest autoconf from bare ubuntu-latest runner

The container `ubuntu:22.10` does not seem to work anymore.

Also, why pin a version of `autoconf`?
Shouldn't we test with the native `autoconf` shipped with the OS?

.github/workflows/haskell.yml

@@ -6,13 +6,13 @@ on:
   pull_request:
     branches: [ 'master' ]
 
-env:
-  autoconf_ver: 2.69
+# env:
+#   autoconf_ver: 2.69
 
 jobs:
   autoconf:
     runs-on: ubuntu-latest
-    container: ubuntu:22.10
+    # container: ubuntu:22.10
 
     steps:
     - uses: actions/checkout@v4