CI: test.yml - Windows - add mswin, remove 3.4 exclude

Author: MSP-Greg

.github/workflows/test.yml

@@ -25,9 +25,10 @@ jobs:
             ruby: truffleruby
           - os: windows-latest
             ruby: truffleruby-head
-          # Remove it once https://github.com/ruby/setup-ruby/issues/680 is fixed
+        include:
           - os: windows-latest
-            ruby: 3.4
+            ruby: mswin
+
     runs-on: ${{ matrix.os }}
     steps:
     - uses: actions/checkout@v4 # v3.3.0