Update test matrix to exclude special cases

Author: warmwaffles

.github/workflows/ci.yml

@@ -17,7 +17,7 @@ jobs:
     strategy:
       matrix:
         os: ["ubuntu-latest"]
-        elixir: ["1.17"]
+        elixir: ["1.18"]
         otp: ["28"]
     steps:
       - uses: actions/checkout@v4
@@ -48,13 +48,19 @@ jobs:
       fail-fast: false
       matrix:
         os: ["ubuntu-latest"]
-        elixir: ["1.17", "1.16", "1.15"]
+        elixir: ["1.18", "1.17", "1.16", "1.15"]
         otp: ["28", "27", "26", "25"]
         exclude:
           - elixir: "1.15"
             otp: "27"
           - elixir: "1.16"
             otp: "27"
+          - elixir: "1.15"
+            otp: "28"
+          - elixir: "1.16"
+            otp: "28"
+          - elixir: "1.17"
+            otp: "28"
         include:
           - os: "windows-2019"
             otp: "27"