Replace Ruby < 2.7 with Ruby 2.7 in CI.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: dblock

.github/workflows/test.yml

@@ -14,20 +14,20 @@ jobs:
     strategy:
       fail-fast: true
       matrix:
-        ruby: [2.5, 2.6, 2.7, 3.0, jruby] # truffleruby
+        ruby: [2.7, 3.0, jruby] # truffleruby
         mongoid: [7]
         experimental: [false]
         include:
-          - ruby: 2.3
+          - ruby: 2.7
             mongoid: 3
             experimental: false
-          - ruby: 2.4
+          - ruby: 2.7
             mongoid: 4
             experimental: false
-          - ruby: 2.5
+          - ruby: 2.7
             mongoid: 5
             experimental: false
-          - ruby: 2.6
+          - ruby: 2.7
             mongoid: 6
             experimental: false
           - ruby: 2.7