CI: Exclude Ruby 2.4 and 2.5 on macOS

Author: mrkn

.github/workflows/ci.yml

@@ -25,22 +25,24 @@ jobs:
         - macos-latest
         - windows-latest
         ruby:
-        - 3.4
-        - 3.3
-        - 3.2
-        - 3.1
-        - 3.0
-        - 2.7
-        - 2.6
-        - 2.5
-        - 2.4
+        - "3.4"
+        - "3.3"
+        - "3.2"
+        - "3.1"
+        - "3.0"
+        - "2.7"
+        - "2.6"
+        - "2.5"
+        - "2.4"
         - debug
         include:
         - { os: windows-latest , ruby: mingw }
         - { os: windows-latest , ruby: mswin }
         exclude:
-        - { os: windows-latest , ruby: 3.0 }
+        - { os: windows-latest , ruby: "3.0" }
         - { os: windows-latest , ruby: debug }
+        - { os: macos-latest , ruby: "2.5" }
+        - { os: macos-latest , ruby: "2.4" }
 
     steps:
     - uses: actions/checkout@v2