CI: run tests on macOS with the latest Go version

.github/workflows/CI.yml

diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index 260e2f1..d62689a 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -15,7 +15,7 @@
         go: ['1.26', '1.25']
         exclude:
           - os: macos-latest
-            go: '1.26'
+            go: '1.25'
 
     steps:
       - uses: actions/checkout@v7