Update Erlang CI matrix

Author: starbelly

.github/workflows/main.yml

@@ -15,7 +15,7 @@ jobs:
 
     strategy:
       matrix:
-        otp_version: [23, 24, 26]
+        otp_version: [26, 27, 28]
         os: [ubuntu-20.04] # latest only runs >= 24.2
 
     container: