update test matrix

Author: binaryseed

.github/workflows/elixir.yml

@@ -19,14 +19,14 @@ jobs:
     strategy:
       matrix:
         include:
-          - elixir: '1.18'
-            otp: '27'
-          - elixir: '1.17'
-            otp: '27'
-          - elixir: '1.16'
-            otp: '26'
-          - elixir: '1.15'
-            otp: '26'
+          - elixir: "1.19"
+            otp: "28"
+          - elixir: "1.18"
+            otp: "27"
+          - elixir: "1.17"
+            otp: "26"
+          - elixir: "1.16"
+            otp: "26"
 
     steps:
     - name: Checkout