Update github actions to run only on still supported ruby versions

Author: JonathanTron

.github/workflows/CI.yml

@@ -4,6 +4,7 @@ on:
   push:
     branches:
       - master
+      - metrilio
   pull_request:
   schedule:
     - cron: '0 1 * * SUN'
@@ -16,15 +17,10 @@ jobs:
       matrix:
         ruby:
           - head
+          - '4.0'
+          - '3.4'
           - '3.3'
           - '3.2'
-          - '3.1'
-          - '3.0'
-          - '2.7'
-          - '2.6'
-          - '2.5'
-          - '2.4'
-          - '2.3'
           - jruby
           - truffleruby-head
     continue-on-error: ${{ matrix.ruby == 'head' }}