Use OTP v26 with Elixir 1.16.x

See: https://hexdocs.pm/elixir/compatibility-and-deprecations.html#between-elixir-and-erlang-otp

Author: sgerrand

.github/workflows/ci.yml

@@ -55,7 +55,7 @@ jobs:
             otp: 26
             os: ubuntu-22.04
           - elixir: 1.16.x
-            otp: 27
+            otp: 26
             os: ubuntu-latest
             warnings_as_errors: true
     env:
@@ -97,7 +97,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: erlef/setup-beam@v1
         with:
-          otp-version: 27
+          otp-version: 26
           elixir-version: 1.16.x
       - name: Install Dependencies
         run: |