Update to copier boilerplate for this project.

See
https://gitlab.com/gitlab-com/gl-infra/common-template-copier
for further details.

chore: copier boilerplate update to v1.13.0

See merge request !127

This change attempts to ensure that written YAML fixtures match the
formatting standards used at GitLab. This can help reduce diff size
between old fixtures and newly written ones.

As requested by @skarbek

feat: use yamlfmt to format written fixtures

See merge request !128