Update Mattermost to 6.6.1
Update Mattermost to 6.6.1

Changelog: other

Signed-off-by: Mustafa Kara <664f6ba1fc1972fbfc33e7e4c8d4a172076cf62b@pinchflat.dev>

gitlabhq/omnibus-gitlab,gitlabhq/omnibus-gitlab,gitlabhq/omnibus-gitlab,gitlabhq/omnibus-gitlab