repository check doc: fix a broken link
repository check doc: fix a broken link

The link to the repocheck.log section of the logs documentation was
added in 7d9191eeff9 ("Small documentation reformatting and updates",
2018-04-23), but seemingly never worked. The markdown formatter turns
"." into "-" in headings.

See
https://docs.gitlab.com/ee/administration/repository_checks.html#what-to-do-if-a-check-failed
which has a broken link to
https://docs.gitlab.com/ee/administration/logs.html#repocheck.log
linking to
https://docs.gitlab.com/ee/administration/logs.html#repocheck-log
instead (just change "." to "-") fixes it.

dreampet/gitlab,mmkassem/gitlabhq,axilleas/gitlabhq,iiet/iiet-git,mmkassem/gitlabhq,axilleas/gitlabhq,stoplightio/gitlabhq,axilleas/gitlabhq,mmkassem/gitlabhq,mmkassem/gitlabhq,iiet/iiet-git,stoplightio/gitlabhq,dreampet/gitlab,axilleas/gitlabhq,dreampet/gitlab,stoplightio/gitlabhq,iiet/iiet-git,stoplightio/gitlabhq,dreampet/gitlab,iiet/iiet-git