patch conda-installed pip with 'conda update pip' update message

[kalefranz]

See comment at pypa/pip#5326 (comment)

It's unfortunate that vendors, when packaging pip for use in system packages, don't patch the message to describe the correct command to use to upgrade the system pip.

Apparently it's recommended that the pip outdated message and how to update pip when it is outdated be patched over.

Technically, I guess that would mean pip would have to ask conda if a newer version is available, and then if so, give a conda update pip message.

[kalefranz]

Another reference: pypa/pip#5346

[nehaljwani]

The detection logic is itself upstream now: pypa/pip#5368