[2.7] Improve ensurepip's --help (GH-4686) (GH-7240)

* Add a space to ensurepip's --altinstall option
* Add periods to the arguments of ensurepip that didn't have it

This makes --help for all optional arguments consistent and also makes it
consistent with pip --help..
(cherry picked from commit e9537ad6a128924dd610bea2268065500c174181)

Co-authored-by: Wieland Hoffmann <mineo@users.noreply.github.com>
1 file changed