Separate test workflow for Ruby 2.2.10

Ruby 2.2.10 cannot be installed on the latest Ubuntu but the Ubuntu 20.04.

Reference: GitHub / ruby / setup-ruby / Bundler install appears broken
           on Ruby 2.2 / the summary comment by eregon [1]

Error output:

  Installing Bundler
    Bundler 2 requires Ruby 2.3+, using Bundler 1 on Ruby <= 2.2
    /opt/hostedtoolcache/Ruby/2.2.10/x64/bin/gem install bundler -v ~> 1.0
    ERROR:  While executing gem ... (RuntimeError)
        Marshal.load reentered at marshal_load
    Took   0.28 seconds

[1] ruby/setup-ruby#496 (comment)

.github/workflows/test.yaml

@@ -4,7 +4,7 @@ on:
   pull_request:
 
 jobs:
-  test:
+  test: &test
     runs-on: ubuntu-latest
 
     strategy:
@@ -14,7 +14,6 @@ jobs:
         - 1.9.3
         - 2.0.0
         - 2.1.9
-        - 2.2.10
         - 2.3.8
         - 2.4.10
         - 2.5.9
@@ -37,3 +36,15 @@ jobs:
 
       - name: Run tests
         run: bundle exec rake
+
+  # Bundler with Ruby 2.2.10 doesn't work for the latest Ubuntu.
+  # See also: https://github.com/ruby/setup-ruby/issues/496#issuecomment-1625000309
+  test-ruby-2.2.10:
+    <<: *test
+
+    runs-on: ubuntu-20.04
+
+    strategy:
+      matrix:
+        ruby-version:
+          - 2.2.10