Revert "[MLX] Raise default macOS deployment target to 26.2 for NAX" (#24868)

Reverts #24803

Author: metascroy

CMakePresets.json

@@ -392,7 +392,7 @@
       "cacheVariables": {
         "EXECUTORCH_BUILD_PRESET_FILE": "${sourceDir}/tools/cmake/preset/mlx.cmake",
         "EXECUTORCH_ENABLE_LOGGING": "ON",
-        "CMAKE_OSX_DEPLOYMENT_TARGET": "26.2"
+        "CMAKE_OSX_DEPLOYMENT_TARGET": "14.0"
       },
       "condition": {
         "lhs": "${hostSystemName}",