CI: drop Ruby 3.1, add Ruby 3.4

Ruby 3.1 is EOL, so remove the 3.1 x Rails 7.2 cell. Add Ruby 3.4 against
Rails 8.0 and 8.1 to cover the new currently-supported release alongside
3.3 and 4.0.

Author: jarednorman

.github/workflows/test.yml

@@ -19,6 +19,12 @@ jobs:
           - rails_version: ~> 8.1.0
             ruby_version: '4.0'
             sqlite_version: ~> 2.0
+          - rails_version: ~> 8.1.0
+            ruby_version: '3.4'
+            sqlite_version: ~> 2.0
+          - rails_version: ~> 8.0.0
+            ruby_version: '3.4'
+            sqlite_version: ~> 2.0
           - rails_version: ~> 8.0.0
             ruby_version: '3.3'
             sqlite_version: ~> 2.0
@@ -28,9 +34,6 @@ jobs:
           - rails_version: ~> 7.2.0
             ruby_version: '3.2'
             sqlite_version: ~> 2.0
-          - rails_version: ~> 7.2.0
-            ruby_version: '3.1'
-            sqlite_version: ~> 2.0
           - rails_version: ~> 7.1.0
             ruby_version: '3.3'
             sqlite_version: ~> 1.0