message: Fix typo in git-authentication.md
diff: @@ -44,7 +44,7 @@ most Unix-like systems), and that the correct keys are added (with `ssh-add`).
  Windows uses Pageant for SSH authentication.
  > **Note:** Cargo does not support git's shorthand SSH URLs like
  -> `git@example.com/user/repo.git`. Use a full SSH URL like
  +> `git@example.com:user/repo.git`. Use a full SSH URL like
  > `ssh://git@example.com/user/repo.git`.
  > **Note:** SSH configuration files (like OpenSSH's `~/.ssh/config`) are not
  