Fix to publish-to-pypi script in response to pypi api change

[dmichaels-harvard]

• Fix to dcicutils/scripts/publish_to_pypy.py script. They (pypi) changed their API so this returns
  HTTP 200 even if the package version does NOT exist: https://pypi.org/project/{package_name}/{package_version}
  So without this fix this script thinks the version to publish already exists even when it does not.
  Changed to use this instead: https://pypi.org/pypi/{package_name}/json which returns JSON for ALL versions.

[coveralls]

Pull Request Test Coverage Report for Build 12713218680

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 75.4%

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Totals
Change from base Build 11917477387:	0.0%
Covered Lines:	11439
Relevant Lines:	15171

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💛 - Coveralls