actions: revert to Ubuntu 20.04

IT is depressing... Thanks god we do not build bridges...

Signed-off-by: Matteo Cafasso <[email protected]>

Author: noxdafox

.github/workflows/action.yml

@@ -2,18 +2,23 @@ name: build
 on: [push, pull_request]
 jobs:
   build:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-20.04
     strategy:
       matrix:
+        erlang:
+          - 1:25.3-1
+        elixir:
+          - 1.13.4-1
         rmqref:
           - v3.12.x
     steps:
       - uses: actions/checkout@v2
       - name: Install Erlang and Elixir
         run: |
-          sudo add-apt-repository ppa:rabbitmq/rabbitmq-erlang-25
+          wget https://packages.erlang-solutions.com/erlang-solutions_2.0_all.deb
+          sudo dpkg -i erlang-solutions_2.0_all.deb
           sudo apt update
-          sudo apt install -y erlang elixir-lang
+          sudo apt install -y --allow-downgrades esl-erlang=${{ matrix.erlang }} elixir=${{ matrix.elixir }}
       - name: Run tests
         run: |
           make current_rmq_ref=${{ matrix.rmqref }}