Change CI OTP Elixir test versions

Author: anronin

.github/workflows/main.yml

@@ -12,11 +12,11 @@ jobs:
       matrix:
         include:
           - pair:
-              elixir: "1.13"
-              otp: "24.3.4.10"
+              elixir: 1.15.x
+              otp: 26.x
           - pair:
-              elixir: "1.15"
-              otp: "26.0"
+              elixir: 1.18.x
+              otp: 27.x
     steps:
       - uses: actions/checkout@v3