CLN: remove redundant mac wheel-build code
- [ ] closes #xxxx
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

this code is redundant for wheels built using https://github.com/MacPython/pandas-wheels, as the line https://github.com/matthew-brett/multibuild/blob/266d88fe1e474748cc8a3823dc3934bf55e76383/osx_utils.sh#L306 adds tags for 10.9 and 10.10.

Note: circleci fails as I forgot to turn it off on my fork, after it was turned off upstream