Use MAINTAINERS file in repository in CONTRIBUTING (go-gitea#1489)

* Use MAINTAINERS file in repository because teams are not publicly available

* Use relative link

CONTRIBUTING.md

@@ -81,7 +81,7 @@ The current release cycle is aligned to start on December 25 to February 24, nex
 
 ## Maintainers
 
-To make sure every PR is checked, we have [team maintainers](https://github.com/orgs/go-gitea/teams/maintainers). Every PR **MUST** be reviewed by at least two maintainers (or owners) before it can get merged. A maintainer should be a contributor of Gitea (or Gogs) and contributed at least 4 accepted PRs. A contributor should apply as a maintainer in the [Gitter develop channel](https://gitter.im/go-gitea/develop). The owners or the team maintainers may invite the contributor. A maintainer should spend some time on code reviews. If a maintainer has no time to do that, they should apply to leave the maintainers team and we will give them the honor of being a member of the [advisors team](https://github.com/orgs/go-gitea/teams/advisors). Of course, if an advisor has time to code review, we will gladly welcome them back to the maintainers team. If a maintainer is inactive for more than 3 months and forgets to leave the maintainers team, the owners may move him or her from the maintainers team to the advisors team.
+To make sure every PR is checked, we have [team maintainers](MAINTAINERS). Every PR **MUST** be reviewed by at least two maintainers (or owners) before it can get merged. A maintainer should be a contributor of Gitea (or Gogs) and contributed at least 4 accepted PRs. A contributor should apply as a maintainer in the [Gitter develop channel](https://gitter.im/go-gitea/develop). The owners or the team maintainers may invite the contributor. A maintainer should spend some time on code reviews. If a maintainer has no time to do that, they should apply to leave the maintainers team and we will give them the honor of being a member of the [advisors team](https://github.com/orgs/go-gitea/teams/advisors). Of course, if an advisor has time to code review, we will gladly welcome them back to the maintainers team. If a maintainer is inactive for more than 3 months and forgets to leave the maintainers team, the owners may move him or her from the maintainers team to the advisors team.
 
 ## Owners