Add Ruby v4.0 to external tests.

Author: ioquatix

.github/workflows/test-external.yaml

@@ -11,7 +11,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest]
-        ruby: ['3.3', '3.4']
+        ruby: ['3.3', '3.4', '4.0']
 
     runs-on: ${{matrix.os}}
     env:

.github/workflows/test.yaml

@@ -22,12 +22,13 @@ jobs:
           - '3.2'
           - '3.3'
           - '3.4'
+          - '4.0'
           - ruby-head
           - jruby-head
           - truffleruby-head
         include:
           - os: macos-latest
-            ruby: '3.1'
+            ruby: '4.0'
     runs-on: ${{matrix.os}}
     env:
       CI: spec