switch to macos-14

Author: real-or-random

.github/workflows/ci.yml

@@ -46,9 +46,9 @@ env:
 
 jobs:
   x86_64-macos-native:
-    name: "x86_64: macOS Ventura, Valgrind"
+    name: "x86_64: macOS Sonoma, Valgrind"
     # See: https://github.com/actions/runner-images#available-images.
-    runs-on: macos-13
+    runs-on: macos-14
 
     env:
       CC: 'clang'