Switch from setup-elixir to setup-beam

Author: J3RN

.github/workflows/ci.yml

@@ -25,7 +25,7 @@ jobs:
           version: ${{matrix.emacs_version}}
 
       - name: Setup OTP + Elixir
-        uses: erlef/setup-elixir@v1
+        uses: erlef/setup-beam@v1
         with:
           otp-version: ${{matrix.otp}}
           elixir-version: ${{matrix.elixir}}