Pin macos mkl conda version to fix the cmake build (#61773)
Summary:
Fixes macos build error in master, recently mkl had a upgrade.
CircleCI error:
https://app.circleci.com/pipelines/github/pytorch/pytorch/351645/workflows/d22421c1-bb8f-48fd-9efd-7c0d77f0b083/jobs/14815607
```
Jul 16 11:43:05 CMake Error at /Users/distiller/workspace/miniconda3/lib/cmake/mkl/MKLConfig.cmake:456 (list):
Jul 16 11:43:05 list does not recognize sub-command PREPEND
Jul 16 11:43:05 Call Stack (most recent call first):
Jul 16 11:43:05 /Users/distiller/workspace/miniconda3/lib/python3.7/site-packages/torch/share/cmake/Caffe2/public/mkl.cmake:1 (find_package)
Jul 16 11:43:05 /Users/distiller/workspace/miniconda3/lib/python3.7/site-packages/torch/share/cmake/Caffe2/Caffe2Config.cmake:109 (include)
Jul 16 11:43:05 /Users/distiller/workspace/miniconda3/lib/python3.7/site-packages/torch/share/cmake/Torch/TorchConfig.cmake:68 (find_package)
Jul 16 11:43:05 CMakeLists.txt:5 (find_package)
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/61773
Reviewed By: soulitzer
Differential Revision: D29736742
Pulled By: zhouzhuojie
fbshipit-source-id: 68c5244196f7f7562a6c202157c4ccdcfcb64337
