Bump gitlab-shell to 7.1.3

This includes the change that prints the @username of a user instead
of the full name.

https://gitlab.com/gitlab-org/gitlab-shell/merge_requests/204

GITLAB_SHELL_VERSION

-7.1.2
+7.1.3

changelogs/unreleased/bvl-bump-gitlab-shell-7-1-3.yml

+---
+title: Include username in output when testing SSH to GitLab
+merge_request: 19358
+author:
+type: other