Bump GHA environments to use Ubuntu 22.04 (up from 18.04)

Since some time ago, GH is warning us that the Ubuntu 18.04
environment is deprecated:

"The ubuntu-18.04 environment is deprecated, consider switching to
ubuntu-20.04(ubuntu-latest), or ubuntu-22.04 instead...."

Hence, we are bumping here, to be able to cerify if everything
continues working ok

.github/workflows/ci.yml

@@ -4,7 +4,7 @@ on: [push, pull_request]
 
 jobs:
   test:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-22.04
 
     services:
       postgres: