Update elixir-version in github worksflows to v1.5

Update elixir-version in github worksflows to v1.5

.github/workflows/elixir.yml

@@ -21,7 +21,7 @@ jobs:
     - name: Set up Elixir
       uses: erlef/setup-beam@988e02bfe678367a02564f65ca2e37726dc0268f
       with:
-        elixir-version: '1.12.3' # Define the elixir version [required]
+        elixir-version: '1.5' # Define the elixir version [required]
         otp-version: '24.1' # Define the OTP version [required]
     - name: Restore dependencies cache
       uses: actions/cache@v2