Update Elixir on CI

Author: josevalim

.github/workflows/ci.yml

@@ -11,7 +11,7 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - elixir: "1.18.1"
+          - elixir: "1.19.4"
             otp: "27.1"
             lint: true
           - elixir: "1.15.8"