[Chapel Merge] Remove references to internal PyPI mirror

Branch: refs/heads/master
Revision: 6374efd
Author: lydia-duncan
Log Message:

Merge pull request #16668 from lydia-duncan/removeOldPipMirrorRef

Remove references to internal PyPI mirror
[reviewed by @mppf]

The internal PyPI mirror is not being maintained and as such does not have the
most up to date version of several Python packages. Stop using it.

Modified Files:
M util/build_configs/cray-internal/setenv-hpe-cray-ex-x86_64.bash
M util/build_configs/cray-internal/setenv-xc-aarch64.bash
M util/build_configs/cray-internal/setenv-xc-x86_64.bash

Compare: https://github.com/chapel-lang/chapel/compare/e10f2a57c61d...6374efdd0ce8