change workflow to macos 15

Author: cdueben

.github/workflows/R-CMD-check.yaml

@@ -10,7 +10,7 @@ permissions:
 
 jobs:
   R-CMD-check:
-    runs-on: macos-latest
+    runs-on: macos-15
     name: macOS (R-devel, clang 16)
 
     env: