Remove stuff for Python before 3.8 from install_conda.sh (#110671)
As we only support Python 3.8+ now.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/110671
Approved by: https://github.com/seemethere, https://github.com/huydhn, https://github.com/atalman, https://github.com/malfet, https://github.com/ZainRizvi