CI: fix installation of GHC 8.0 and 8.2.

It seems that libtinfo5 is not installed by default, but it's apparently
required for a successful installation of these versions.

Author: tarleb

.github/workflows/ci.yml

@@ -45,6 +45,7 @@ jobs:
 
     - name: Install cabal/ghc
       run: |
+        sudo apt install libtinfo5 # required for GHC 8.0 and 8.2.
         ghcup install ghc --set ${{ matrix.versions.ghc }}
         ghcup install cabal --set ${{ matrix.versions.cabal }}