revert MacOS CMake cpp to macos-13

Author: Rachel Goldfinger

.github/workflows/test_cpp.yml

@@ -349,7 +349,8 @@ jobs:
       matrix:
         include:
           - name: MacOS CMake
-            os: macos-14
+            os: macos-13
+            flags: -DCMAKE_CXX_STANDARD=14
             cache-prefix: macos-cmake
           - name: Windows CMake
             os: windows-2022