[PIP] Use python tag instead of cpython tag for OSX

[szha]

Description

Use python tag instead of cpython tag for OSX

Checklist

Essentials

• PR's title starts with a category (e.g. [BUGFIX], [MODEL], [TUTORIAL], [FEATURE], [DOC], etc)
• Changes are complete (i.e. I finished coding on this PR)
• All changes have test coverage
• Code is well-documented

Changes

• Remove BinaryDistribution option for OSX builds.

[mxnet-bot]

Hey @szha , Thanks for submitting the PR
All tests are already queued to run once. If tests fail, you can trigger one or more tests again with the following commands:

• To trigger all jobs: @mxnet-bot run ci [all]
• To trigger specific jobs: @mxnet-bot run ci [job1, job2]

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CI supported jobs: [edge, clang, centos-gpu, windows-cpu, windows-gpu, miscellaneous, sanity, centos-cpu, unix-cpu, unix-gpu, website]

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Note:
Only following 3 categories can trigger CI :PR Author, MXNet Committer, Jenkins Admin.
All CI tests must pass before the PR can be merged.