repository check doc: fix a broken link

The link to the repocheck.log section of the logs documentation was
added in 7d9191ee ("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.

doc/administration/repository_checks.md

@@ -31,7 +31,7 @@ panel.
 If the repository check fails for some repository you should look up the error
 in `repocheck.log`:
 
-- in the [admin panel](logs.md#repocheck.log)
+- in the [admin panel](logs.md#repocheck-log)
 - or on disk, see:
     - `/var/log/gitlab/gitlab-rails` for Omnibus installations
     - `/home/git/gitlab/log` for installations from source