fix CI

Author: tiagoefmoraes

.github/workflows/ci.yml

@@ -9,17 +9,15 @@ on:
 jobs:
   mix_test:
     name: mix test (${{format(matrix.blend != '' && 'Blend {0} | Elixir {1} | Erlang/OTP {1}' || 'Elixir {1} | Erlang/OTP {2}', matrix.blend, matrix.elixir, matrix.otp)}})
-    runs-on: ubuntu-latest
     strategy:
       fail-fast: false
       matrix:
         include:
           - elixir: '1.13.4'
             otp: '24.0'
+            os: 'ubuntu-20.04'
             blend: 'lowest'
-          - elixir: '1.13.4'
-            otp: '25.0'
-          - elixir: '1.14.0'
+          - elixir: '1.14.1'
             otp: '25.0'
           - elixir: '1.15.2'
             otp: '26.0'
@@ -35,6 +33,7 @@ jobs:
             otp: '27.3.3'
             blend: 'github'
             warnings_as_errors: true
+    runs-on: ${{ matrix.os || 'ubuntu-latest' }}
     env:
       MIX_ENV: test
       BLEND: ${{ matrix.blend }}