Newer elixir & erlang in CI

Author: PragTob

.github/workflows/main.yml

@@ -44,8 +44,8 @@ jobs:
             otp_version: '28.3'
             type_check: true
             lint: true
-          - elixir_version: '1.20.0-rc.4'
-            otp_version: '28.3'
+          - elixir_version: '1.20.0-rc.6'
+            otp_version: '29.0'
 
     steps:
       - name: Checkout