Update elixir.yml

Author: princemaple

.github/workflows/elixir.yml

@@ -14,7 +14,7 @@ jobs:
     steps:
     - uses: actions/checkout@v2
     - name: Setup elixir
-      uses: erfel/setup-elixir@v1
+      uses: erlef/setup-elixir@v1
       with:
         elixir-version: "1.11"
         otp-version: "23"