Fix IndentationError in setup.py

[zachgk]

Description

Fix the setup.py file indentation error in CD (http:https://jenkins.mxnet-ci.amazon-ml.com/blue/organizations/jenkins/restricted-mxnet-cd%2Fmxnet-cd-release-job/detail/mxnet-cd-release-job/186/pipeline).

@samskalicky @vrakesh @lanking520

Checklist

Essentials

Please feel free to remove inapplicable items for your PR.

• Changes are complete (i.e. I finished coding on this PR)
• All changes have test coverage:
• Unit tests are added for small changes to verify correctness (e.g. adding a new operator)
• Nightly tests are added for complicated/long-running ones (e.g. changing distributed kvstore)
• Build tests will be added for build configuration changes (e.g. adding a new build option with NCCL)
• Code is well-documented:
• For user-facing API changes, API doc string has been updated.
• For new C++ functions in header files, their functionalities and arguments are documented.
• For new examples, README.md is added to explain the what the example does, the source of the dataset, expected performance on test set and reference to the original paper if applicable
• Check the API doc at https://mxnet-ci-doc.s3-accelerate.dualstack.amazonaws.com/PR-$PR_ID/$BUILD_ID/index.html
• To the my best knowledge, examples are either not affected by this change, or have been fixed to be compatible with this change

[samskalicky]

LGTM

[leezu]

Following this PR, headers are only copied on OSX platform, which doesn't make any sense. @zachgk what's your intention here?

[leezu]

cc @lanking520 @vrakesh and @samskalicky who approved this

[leezu]

You should look at the context that introduced the indentation error to see how to fix it

017f6fa#diff-e1b66bb36e566bfd108d2ef312defbd9