Update MacOS runner

Updates the MacOS runners to use latest intel

Signed-off-by: Sudha Parimala <sudharg247@gmail.com>

Author: Sudha247

.github/workflows/build.yml

@@ -12,7 +12,7 @@ jobs:
     strategy:
       matrix:
         include:
-          - os: macos-13
+          - os: macos-15-intel
             name: x86_64-apple-darwin
             output: .#dune.dynamic
           - os: macos-14