Fixup passphrase vs password wording on ssh-create.page

Passphrase is used to refer to the one built-in to the key itself:
https://help.github.com/articles/working-with-ssh-key-passphrases
Help: Add password-free SSH steps on ssh-create.page

* Add a section :"Create your key and install it on a remote computer"
which details the steps for sending the public ssh key to a remote
for password-free login.
* Use "log in" as a verb, and "login" as a noun.