Fix deprecation warning for mix

Author: dmarcoux

.github/workflows/continuous_integration.yml

@@ -73,7 +73,7 @@ jobs:
 
       - name: Install and compile dependencies
         if: steps.cache.outputs.cache-hit != 'true'
-        run: mix do deps.get, deps.compile
+        run: mix do deps.get + deps.compile
 
       - name: Find unused dependencies # https://hexdocs.pm/mix/Mix.Tasks.Deps.Unlock.html
         run: mix deps.unlock --check-unused