gitlab: Sync gitlab-parameters.cfg to upstream

I manually reviewed

    $ git diff 8.4.2+ce.0-3-g68d5ee8..8.5.1+ce.0-1-ge732b39 \
        files/gitlab-config-template/gitlab.rb.template \
        files/gitlab-cookbooks/gitlab/attributes/default.rb

in omnibus-gitlab, and module proxy_set_header change, which we already
addressed in previous patch in Nginx config, there are no more changes
for us.

software/gitlab/gitlab-parameters.cfg

@@ -6,7 +6,7 @@
 #
 # TODO better autogenerate from ^^^ (?)
 #
-# (last updated for omnibus-gitlab 8.4.2+ce.0-3-g68d5ee8)
+# (last updated for omnibus-gitlab 8.5.1+ce.0-1-ge732b39)
 
 [gitlab-parameters]
 configuration.external_url              = http://lab.example.com

software/gitlab/software.cfg

@@ -235,7 +235,7 @@ md5sum  = d8b3611386c4982605edd9a31832ee28
 
 [gitlab-parameters.cfg]
 <= download-file
-md5sum  = 2cfd3bbf9da10627044ca3a9a149fdbb
+md5sum  = b04b72949f0b9b5da96870ffbf8c1ff4
 
 [gitlab-shell-config.yml.in]
 <= download-template