Docs: fix spacing in ext gitaly doc
Fix the spacing on the external Gitaly docs, so that they appear correctly on docs.gitlab.com
(https://docs.gitlab.com/charts/advanced/external-gitaly/index.html)
Fix the spacing on the external Gitaly docs, so that they appear correctly on docs.gitlab.com
(https://docs.gitlab.com/charts/advanced/external-gitaly/index.html)