Fix the way to specify extra jobs

Author: k0kubun

.github/workflows/macos.yml

@@ -34,12 +34,12 @@ jobs:
     strategy:
       matrix:
         test_task: ['check'] # "test-bundler-parallel", "test-bundled-gems"
-        # specifying everything else with `include` to avoid redundant tests
+        os: [macos-12]
+        configure: ['--enable-shared']
+        # specifying other jobs with `include` to avoid redundant tests
         include:
           - os: macos-11
             configure: ''
-          - os: macos-12
-            configure: '--enable-shared'
       fail-fast: false
 
     env:

.github/workflows/ubuntu.yml

@@ -36,7 +36,7 @@ jobs:
         test_task: [check]
         arch: ['']
         configure: ['cppflags=-DVM_CHECK_MODE']
-        # specifying everything else with `include` to avoid redundant tests
+        # specifying other jobs with `include` to avoid redundant tests
         include:
           - test_task: check
             arch: i686