Improve documentation for creating SSH keys

Unless you're a Tichtov student, please do not take this issue, or create an MR for it.

Problem to solve

The Vale linter is used to support grammar linting in GitLab documentation. As Vale was implemented after many of the GitLab documents were written, we have many documentation pages that do not meet the linting standards created by the GitLab Technical Writing team for Vale.

Further details

As an example, here's the output from a Vale test on the doc/gitlab-basics/create-your-ssh-keys.md file:

 doc/gitlab-basics/create-your-ssh-keys.md
 10:1   suggestion  Use "it's" instead of "It is",  gitlab.ContractionsKeep    
                    for a friendly, informal tone.                             
 11:26  warning     Avoid using future tense:       gitlab.FutureTense         
                    "will need"                                                
 28:25  suggestion  Use "can't" instead of          gitlab.ContractionsKeep    
                    "cannot", for a friendly,                                  
                    informal tone.                                             
 28:47  suggestion  Use "did not" instead of        gitlab.ContractionsDiscard 
                    "didn't", for a friendly,                                  
                    informal tone.                                             
 29:2   warning     Avoid using future tense:       gitlab.FutureTense         
                    "will not"                                                 
 30:5   warning     Avoid using future tense:       gitlab.FutureTense         
                    "will need"                    

Each of these messages point to a specific line:column in the noted file.

Proposal

Consider each error message, and see if you can rewrite the noted file with a solution.

Who can address the issue

Anyone with an understanding of basic written US English. Ideally, that person should also have some domain expertise in the subject area.

Additional notes

We appreciate any help that you can provide. If you cannot resolve some of the issues, that is OK, your contributions are still appreciated. And thank you!